Compiled from official source data by PlainSchools.
6 public K-12 schools in Mercer Island from NCES Common Core of Data: enrollment, grade span, demographics, and Civil Rights Data Collection statistics for every active campus.
According to NCES CCD 2024-25, Mercer Island has more public-school enrollment than 44% of the 4,487 US cities in this directory. Mercer Island High School enrolls 36.0% of Mercer Island's public-school students. That is enough concentration for one institution to pull the citywide enrollment, staffing, and Resource Index averages toward its own profile. The smaller campuses below should therefore be compared directly rather than inferred from the headline mean; their grade configurations and program footprints can be materially different even inside the same district.
The school portfolio is elementary-weighted
3 of Mercer Island's 6 listed schools are elementary campuses. That composition means citywide enrollment and staffing averages are influenced more by early-grade operating patterns than by the city's 1 middle and 1 high-school records. Families comparing later grades should rely on those individual rows rather than the all-school mean.
One district, but meaningful resource variation
Mercer Island's schools share one district authority while their average Resource Investment Index ranks at the 99th percentile among listed cities. Shared governance removes one source of policy variation, but it does not erase campus differences by grade span or enrollment. The 15-point gap between Northwood Elementary School and Islander Middle School measures the remaining local spread. Use the district-level picture for common budget context, then compare the school components to see whether staffing, counseling, gifted-program reporting, or attendance accounts for each campus's position.
City enrollment
Top 56%
School count
Top 79%
Resource Index average
99th percentile
Teacher staffing
24th percentile
Mercer Island High School accounts for 36.0% of all Mercer Island public-school enrollment
That dominant concentration means Mercer Island-wide averages can mask substantial variation outside the largest entity. Grade level: High. The share measures enrollment concentration only; it does not establish how districts allocate programs, capital, or staff. Enrollment-weighted aggregates give this entity more weight than any smaller peer, while an unweighted entity average treats every record equally.
Mercer Island school enrollment varies 4.0× across entities
Mercer Island school enrollment ranges from 364 students (lowest) to 1,439 students (highest), a spread of 1,075 students. That relatively narrow ratio reflects an unusually homogeneous school portfolio for a city this size. Per-school staffing and program breadth can differ sharply at opposite ends of that enrollment range, so the city average should not be treated as a typical campus.
Mercer Island operates one school district — a single-district system
Mercer Island's listed schools share one district boundary, budget authority, and reporting chain. That makes citywide and districtwide governance easier to compare, but it does not make individual campuses uniform: grade configuration, staffing, programs, and student need can still vary materially within the same school district.
Mercer Island student-teacher ratio is 18.2:1 — high (typically associated with larger urban scale or staffing constraints that have widened the headcount gap)
student-teacher ratio is the simplest comparative metric but it does not capture the full picture: the ratio counts FTE classroom teachers against total enrollment, push-in specialists, English-language aides, special-education co-teachers, and counselors are not included in most reporting Higher values may reflect larger urban scale or recent resource constraints that have widened the gap.
Most racially and ethnically mixed schools in Mercer Island
Ranked by the Simpson student-body diversity index (0-100) from NCES race and ethnicity data, where higher means a more evenly mixed student body. It measures mix, not quality.
What do families ask about schools in Mercer Island?
Which Mercer Island school has the highest Resource Investment Index? ▼
Northwood Elementary School has the highest Resource Investment Index among the Mercer Island schools in this federal-data comparison at 66/100. The index summarizes reported staffing, counseling, gifted-program, and attendance inputs; it is not an academic rating.
How many schools are in Mercer Island, WA? ▼
Mercer Island has 6 public schools with a total enrollment of 3,993 students. Average student-teacher ratio: 18.2:1.
Data from NCES Common Core of Data (CCD) 2024-25 and Civil Rights Data Collection (CRDC) 2021-22. The Resource Investment Index uses reported student-teacher ratio,
counselor access, gifted programs, and attendance; it is not an academic rating. Cities must include at least five schools to be listed. This public-data comparison is for informational purposes:
verify current enrollment, attendance boundaries, and programs with the school district before acting. See the guide to understanding NCES data.
