1 in 3 K-12 Children don’t attend MI School District

Written By Brian Gaspar

Some have questioned the claim that nearly 34% (33.95%) of Mercer Island children do not attend public school, arguing that the island has only 4,700 K–12-aged children. But the facts tell a different story.

According to the Mercer Island School District’s own demographic records, the last time there were 4,700 known K–12 students attending either public or private schools on the island were in 1999—and that figure would be even higher if it accounted for homeschooled children or those attending private schools not surveyed by the district. By 2015, the district’s demographic report recorded 5,042 school-aged children enrolled in public and private schools on Mercer Island—though the actual number may be higher, as some private school students may not have been captured in the district’s survey data. Including a conservative 3% estimate for homeschooled students—the King County average in 2015—brings the total to approximately 5,193 students.

When factoring in a 7.67% population growth rate from 2015 to 2025—based on census trends and city planning data—the projected total number of K–12-aged children on Mercer Island in 2025 is approximately 5,595.

Importantly, data from multiple federal, county, city, and Mercer Island School District sources do not support any claim that the number of school-aged children on the island has declined below 2015 levels. In fact, the most recent U.S. Census data estimates 5,593 children between the ages of 5 and 18 reside on Mercer Island—a number that falls within the Census Bureau’s stated margin of error and affirms continued population stability among K–12-aged children.

In contrast, the Mercer Island School District’s own 2024–25 budget projects 3,815 students, of which 120 are from off-island. That means just 3,695 Mercer Island students are currently enrolled in the district. Final 2024–25 enrollment numbers have not yet been published.

That leaves:

5,593 - 3,695 = 1,898 students,
or
1,898 ÷ 5,593 ≈ 33.95%,

of Mercer Island students attending private or homeschool options

Enrollment Trends from 2019 to 2026

According to the Mercer Island School District’s own demographic projections, the average public school enrollment across multiple cohorts was forecasted at 4,667 students in 2025. If the historical trend of 15% private school attendance remained consistent through 2025—as current data suggests—and 3% of students continue to homeschool in line with King County averages, the total projected number of K–12-aged children on Mercer Island in 2025 would be approximately 5,507.

Notably, the MISD demographic report used a slightly lower population growth rate than what Mercer Island actually experienced. This further reinforces—using MISD’s own data—that the district expected the K–12 student population in 2025 to exceed 5,500. The students didn’t leave the island—they left the public school system. Mercer Island families have increasingly chosen other schooling options, shifting enrollment away from MISD schools, but not from the community itself.

2025 Mercer Island Enrollment Breakdown

Withdrawal Trends Confirm Families Are Leaving

MISD’s own data shows that between February and September 2024, 150 students withdrew from the district, up from 126 in the same period the previous year—a 19% increase. This points to a continuing shift in parent confidence and school selection. In response, the school board and district have attempted to offset these losses through open enrollment, which now accounts for 5.1% of total district enrollment in grades that allow it for the 2024–2025 school year.

Part of a Broader Statewide Shift

Washington now leads the country in the growth of private school enrollment—even after the pandemic peak. Homeschooling, too, has risen significantly in King County.

Sources

Conclusion

The claim that only 4,700 school-aged children live on Mercer Island hasn’t been accurate since at least 1999—and contradicts both historical and current data. In reality, the parents of 1,898 students—roughly one in three families—have chosen to opt out of Mercer Island’s public schools in favor of private education or homeschooling.

Understanding why families are leaving is not just important—it’s urgent. The future of our schools depends on it.

Brian Gaspar http://www.apokto.com
Next

Fact Check: Superintendent Rundle’s 2025 Letter to the Community