When Evergreen Public Schools tells the community a school is operating at 76.5% of capacity — or 56.2%, or 98.0% — what exactly is being measured? The honest answer surprises most people. Functional capacity is not a measurement of a building. It is a calculation, and the same school can carry wildly different numbers depending on which formula a district chooses to use.
This guide walks through how the math actually works, using three EPS schools as worked examples: Harmony Elementary, near full at 94.7%; Pacific Middle School, slightly over at 98.0%; and Mountain View High School, well under at 56.2%. Along the way it explains the five competing definitions of "capacity," the two dominant calculation models, and why districts from Chicago to Seattle to Vancouver have all fought public battles over the same underlying question: how full is full?
Five definitions, not one
The Association for Learning Environments (A4LE), formerly the Council of Educational Facility Planners International, is the closest thing to an industry standards body for school facility planning. A4LE defines school capacity as "the number of learners that can be reasonably accommodated by a school, building, and site" — and immediately notes that this number depends on which of five different definitions a district chooses to apply.
Each definition layers in additional real-world constraints. A building's theoretical maximum keeps shrinking as you account for support facilities, scheduling realism, special programs, and finally portables. Districts almost always operate somewhere between functional capacity (the middle step) and program capacity (one step deeper).
Functional capacity sits in the middle of the spectrum — discounted for scheduling, but not yet for any specific program decisions. It is the metric most districts publish, and the one EPS uses in its school-by-school utilization tables.
The two formulas
Across consultants and districts, two methodologies dominate the calculation of functional capacity. Most thorough capacity studies actually compute both, then reconcile them. The two approaches answer the same question — "how many students can this building reasonably hold?" — from different starting points.
Teaching Stations × Target Class Size × Utilization Factor
Total Instructional Sq Ft ÷ Sq Ft per Student Standard
Variation comes from three places: which rooms count as "teaching stations" (specials? gyms? labs?), what class size is assumed, and what utilization factor applies. Districts disclose these inputs differently — when they disclose them at all.
Two formulas, three judgment calls, one number on a public report. The methodology is rarely shown.
Worked example: Harmony Elementary
EPS publishes Harmony Elementary's functional capacity as 432 students. With 409 students attending in 2025-26, the school operates at 94.7% utilization — one of the most full elementary schools in the district. To understand what that 432 represents, we can reverse-engineer it using the Model A approach typical for elementary schools.
Elementary schools use a simpler version of Model A than secondary schools because students stay with their homeroom teacher most of the day. The teaching-station count is essentially the count of self-contained classrooms — specials rooms (music, art, library, gym) generally do not count toward capacity at the elementary level under A4LE conventions.
Now compare Harmony's calculation to the formula Chicago Public Schools uses, which is one of the most publicly-documented in the country:
"Ideal Capacity = floor(Number of Classrooms × 77%) × 30. The 77% reflects an assumption that 23% of classrooms are 'ancillary' (art, computer lab, etc.). The 30 is the assumed class size midpoint."
The CPS formula and the EPS formula land in similar territory — both treat the elementary classroom count as the raw input, both apply some discount (CPS via the 77% factor, EPS implicitly through its standard of service), and both multiply by a class-size target. The numbers come out close enough that Harmony's 432 is consistent with how the rest of the country calculates capacity for an 18-classroom elementary school.
432 isn't a measurement of Harmony Elementary. It's the output of a formula EPS chose to apply.
The 85% utilization factor
The single most important variable in any functional capacity calculation is the utilization factor — the percentage of theoretical maximum capacity that the district treats as practically achievable. This is the number that accounts for teacher prep periods, planning time, scheduling friction, and the simple fact that no classroom is in active instructional use 100% of the day.
Across the country, an informal consensus has settled around 85% for middle and high schools and 90-100% for elementary schools. The 85% number appears in capacity reports from Portland, Denver, Seattle, and San Antonio — and it is roughly consistent with general facilities-management practice, where 80-85% is the canonical target for any high-utilization asset.
"That 90-percent rule of thumb? It's a nice formula, but it is just that — a model, not a reflection of the actual activity of the school."— Paul Abramson, CEFPI 2008 Planner of the Year, in School Planning & Management
Abramson's broader argument is that utilization rates are useful planning shorthand but should never be treated as objective measurements. Two elementary schools with identical buildings and identical enrollments can have different "real" utilization depending on how many SPED clusters they host, how their dual-language strands are configured, and whether their cafeteria can run two lunches or three.
85% is a planning convention, not a property of a building. EPS using 80% as its green threshold is a policy choice — a slightly more lenient one than most peers.
Three EPS schools, three stories
EPS's April 23, 2026 Budget Committee facilities study published functional capacity and 2025-26 attending enrollment for every operating school in the district. The numbers tell three different stories at three different grade levels — and each story has different operational implications for the district.
Each scenario carries different operational consequences. Harmony's 94.7% means most rooms are scheduled most periods; the building is producing close to its design value, but adding even a single additional class requires creative scheduling or a portable. Pacific's 98.0% exceeds the practical maximum the formula assumes — the school has no slack for the kind of normal scheduling friction the 85% utilization factor was designed to absorb. Mountain View's 56.2% means roughly 1,100 unfilled seats, equivalent to the cost of operating an entire small elementary school for students who aren't there.
Elementary average: 76.5% · Middle School average: 72.1% · High School average: 59.8%. District-wide, EPS operates roughly 19,000 functional seats against approximately 14,500 attending students.
The same district contains schools at 56% and 98% in the same year. The functional capacity number is identical in form for both, but the meaning in each building is entirely different.
Where the math goes soft
Functional capacity calculations look precise on a printed page — three or four digits, no decimals, neat percentages — but the underlying methodology contains real ambiguity. Three issues recur in every district that has tried to use functional capacity as the basis for a closure decision.
First, special-education and program rooms get treated inconsistently. A self-contained SPED classroom serving 8 students occupies the same physical room as a general education classroom serving 25 — but it generates only 8 seats of capacity, not 25. Some districts deduct these rooms before applying the utilization factor; others don't. The same building can carry a 10-15% different functional capacity depending on this single decision.
Parents alleged in Swan v. Board of Education of Chicago that the district's utilization formula systematically undercounted special-education classroom needs, producing artificially low utilization numbers at schools serving more students with disabilities. CPS later revised its formula to add an "Adjusted Utilization 2" calculation that treats cluster classrooms as 0.5 classrooms.
Second, design capacity ages poorly. A school built in 1985 for 600 students using 1985-era educational programs may have a 2025 functional capacity that is 100 or more students lower — not because the building shrank, but because programs that didn't exist in 1985 (modern SPED inclusion, English Language Learner pull-outs, technology rooms, intervention spaces) now occupy rooms that used to be general classrooms.
Third, the methodology becomes contested as soon as money is on the line. The same number that a district can publish for years without scrutiny suddenly becomes a target the moment it is used to justify a closure or consolidation. Three recent examples illustrate the pattern:
Seattle Public Schools (2024) — Used the framing "elementary schools are at 65% utilization, plan moves to 85%" to propose closing approximately 20 elementaries. The plan was withdrawn after sustained community challenge to the methodology.
San Francisco Unified (2024) — Hired a consultant for $30,000 to develop an "equity-centered" closure formula that incorporated facility utilization, test scores, geography, and equity weights. After the closure list was released, the superintendent resigned, and the plan was shelved indefinitely.
Chicago Public Schools (2013) — Closed approximately 50 schools justified primarily by "underutilization." Parents sued over the formula's treatment of special education. The district later widened its "efficient" range from 80-120% to 70-110% in response to community feedback.
In every contested closure, the functional capacity number itself became the argument. The math is only as defensible as the methodology behind it — and the methodology is rarely shown.
How EPS does it
The Office of Superintendent of Public Instruction (OSPI) does not publish a functional capacity formula for Washington school districts. Instead, OSPI maintains a Student Space Allocation (SSA) — a square-feet-per-student standard used to determine state matching funds for new construction. The SSA is a Model B formula. It tells a district how much space the state will help pay for; it does not tell the district how full any given school is.
That gap is filled by each district's own methodology. Evergreen Public Schools' approach is documented in its Capital Facilities Plan, filed with Clark County under the Growth Management Act. The CFP defines the district's "standard of service" — the local equivalent of functional capacity:
"The District's standard of service is based on program year, class size by grade span, number of classrooms, types of facilities, and the District's adopted educational program."
This is functionally equivalent to the A4LE program-capacity definition: it starts with class size and classroom count, then adjusts for the district's adopted educational program. The advantage is that it is locally specific and transparent about what it is measuring. The limitation is the same one every district faces — when "adopted educational program" changes (a new SPED inclusion model, a new dual-language strand, a new intervention block), the underlying capacity changes too, but the published number often does not catch up immediately.
The April 2026 Budget Committee study marked the first time EPS published school-by-school functional capacity figures alongside both attending enrollment and residing-boundary enrollment. That methodological transparency is what makes the kind of public conversation in this guide possible. The next questions — which schools should be the focus of any future facility planning, what closure or consolidation actually saves, and whether EPS's 80% green threshold should be tightened to match peers — depend on having that baseline data in public view.
Functional capacity is a contract between a district and its formula. Reading it well requires reading both.