As of the 2022–23 school year, the school had an enrollment of 1,524 students and 74.51 classroom teachers (on an FTE basis), for a student–teacher ratio of 20.45. There were 68 students eligible for free lunch and 31 eligible for reduced-cost lunch.[1]
MIHS adopted a cell-phone free policy in the 2024-25 school year. In the 2025-26 school year the policy was expanded to include personal laptops and tablets.[4][5]
In 2025, reporting by InvestigateWest and statements from King County prosecutors brought renewed attention to past allegations of sexual misconduct involving two former teachers at Mercer Island High School. The coverage also examined the district’s handling of those cases and its internal review processes (see Sexual misconduct allegations).[6][7]
The school's marching band has traveled to play at national and international events. It participated in the 104th annual Rose Parade in Pasadena, California, in 1993;[10][11] the 117th edition in 2006;[12] the 123rd edition in 2012;[13] and the 130th edition in 2019.[14]
In 2011, the band traveled internationally to participate in the 2011 London, EnglandNew Year's Day Parade & Festival upon royal invitation.[15] In 2014, the marching band participated in the 116th Victoria Day parade in Victoria, British Columbia; they returned in 2017 for the 119th Victoria Day parade.[16][17] In 2015, members of the marching and concert bands traveled to Australia as part of a tour including participation in the Australian National Band Championships.[18][19]
Girls' Swim and Dive had an undefeated season in 2009 ending it by winning the State Championship. Boys' Swim and Dive also went undefeated in the 2009-2010 season, and went on to win their fifth consecutive State title.
The girls' and boys' tennis teams have won a combined 41 State championships since 1972.[26] The girls tennis team has won 25 state titles and has been inducted into the Washington Interscholastic Activities Association Hall of Fame.[27]
The basketball team, formerly coached by all-time Washington state wins leader Ed Pepple,[28] recorded its first losing season in 38 years in 2006.
In 1981 Mercer Island Basketball Team lost the AAA State basketball final game to Shadle Park in a controversial decision.[29] At 64-65 to Mercer Island, a last-second shot by Shadle Park "depending on who you are listening to, either clearly did or clearly didn’t beat the air horn."[30][31]
Boys' swimming was rated first in its class by the 2006-07 NISCA National Dual Meet Team Rankings.[32]
In the 2024/2025 season, on Saturday, November 9, 2025, at Sun Willows Golf Course in Pasco, Washington, the Mercer Island Cross Country Team won both the Girls XC AAA State Championship and the Boys XC AAA State Championship. The girls were led by the Rodriguez sisters. The sophomore Sophia and the senior Victoria who were invaluable to the team's success. Senior Owen Powell, junior Bodie Thomas, and sophomore Mathew Strong were the dynamic trio who propelled the boys to victory.[33] Particularly Owen Powell who became the first high school athlete from Washington State to run a sub-4-minute mile. He clocked a time of 3:57.74 at the University of Washington Husky Classic, breaking the previous state high school record of 4:01.50 set by Olympian Gerry Lindgren in 1964. This happened after cross country season on February 21, 2025 at an indoor track.[34]
In the 2024/2025 season, on Saturday, May 24, 2025, at Starfire Stadium in Tukwila, Washington, the Mercer Island Boys Lacrosse team clinched the 3A title with an 11–8 victory over Bellevue High School. This win was particularly significant as Mercer Island avenged its only loss of the season, which had come against Bellevue.
Since 2011, the unofficial school mascot has been a maroon-and-white snail named Herbert.[3] The “tropical warrior” Islander mascot of the ‘70s was deemed to be offensive and has not been used since.[35]
Sexual misconduct allegations
In 2025, InvestigateWest published reports describing past allegations of sexual misconduct by two teachers at Mercer Island High School (MIHS) and the district’s handling of those cases.[6][7]
According to the reporting, King County prosecutors stated that they found credible evidence that teacher Gary “Chris” Twombley had engaged in sexual contact with a student in 2015 but did not file charges because the statute of limitations had expired. The articles also stated that internal district records indicated the district did not make the allegations public or conduct a full investigation at the time.[6]
A separate report detailed allegations against teacher Curtis Johnston, who a former student said had a sexual relationship that began while she was a senior and continued after graduation. Documents cited in the article described the district’s 2011 internal review as limited in scope and focused on personnel and legal considerations rather than a formal investigation.[7]
The district has not disputed the existence of the prior internal reviews but has stated that no evidence available at the time supported disciplinary action. Publication of the 2025 articles prompted renewed public discussion about the district’s procedures for responding to misconduct allegations.
1 2 Staff. "A snail sighting", Mercer Island Reporter, January 14, 2011. Accessed June 6, 2017. "Mercer Island High School senior Teddy Trimble is ‘Herbert the Snail,’ the Islander mascot never before seen in physical form, at its very first appearance on Friday night at the boys and girls basketball games."
↑ "Archived copy"(PDF). Archived from the original(PDF) on September 28, 2011. Retrieved May 15, 2012.{{cite web}}: CS1 maint: archived copy as title (link) retrieved May 14, 2012.
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