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]
The school’s marching band has received national and international attention. In 1993 it participated in the 104th Rose Parade.[6][7] In 2006, the marching band returned to Pasadena for the 117th Rose Parade.[8] In 2011, the band traveled internationally to participate in the 2011 London, EnglandNew Year’s Day Parade & Festival upon royal invitation.[9][10][11][12][13][14][15][16] The following year, the marching band performed in the 2012 Rose Parade.[17] That fall, the band performed along with Newport High School at halftime of the November 4 Seattle Seahawks football game versus the Minnesota Vikings.[18] In the spring 2014, the marching band participated in the 116th Victoria Day parade in Victoria, British Columbia.[19] That fall, Mercer Island, Newport, and Cedarcrest High School performed at halftime of the December 14 Seahawks game versus the San Francisco 49ers.[20] 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.[21][22] In 2017, the marching band returned to Victoria to participate in the 119th Victoria Day Parade.[23] In 2019, the marching band again participated in the Rose Parade.[24][25] The marching band performed at a special halftime performance at the October 10, 2019 Seahawks game against the Los Angeles Rams, honoring longtime team owner and Mercer Island resident Paul G. Allen.[26] In 2020, the band was scheduled to perform at the 123rd Victoria Day parade but the event was cancelled due to the COVID-19 pandemic. On September 19, 2021, the band performed at the 2021 Seahawks opening home game, performing before the game and appearing at halftime alongside Macklemore and singer-guitarist Ayron Jones. In November 2023, the band participated in the 97th Annual Macy's Thanksgiving Parade.
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.[29] The girls tennis team has won 25 state titles and has been inducted into the Washington Interscholastic Activities Association Hall of Fame.[30]
The basketball team, formerly coached by all-time Washington state wins leader Ed Pepple,[31] 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.[32] 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."[33][34]
Boys' swimming was rated first in its class by the 2006-07 NISCA National Dual Meet Team Rankings.[35]
The “tropical warrior” Islander mascot of the ‘70’s was deemed to be offensive and has not been used since.[36]
^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 2011-09-28. Retrieved 2012-05-15.{{cite web}}: CS1 maint: archived copy as title (link) retrieved May 14, 2012.
^Matt Boyd, Oregon State Beavers baseball. Accessed September 16, 2019. "Mercer Island High School - Played his freshman season, 2005-06, for head coach Doug Williams"
^Meet Steve Bunin, KING-TV, updated August 28, 2019. Accessed September 16, 2019. "I have three brothers, and graduated from Mercer Island High School in 1992 and Syracuse University in 1996."
^Brewer, Jerry. "Montana’s new coach very much a product of Seattle basketball", The Seattle Times, November 22, 2014. "He’s a product of Seattle basketball in every way imaginable, from his Rainier Valley upbringing to his days as a star guard at Mercer Island High School to his first head-coaching job at Sammamish High School to his junior-college experience at Green River Community College."
^Ko, Michael. "Basketball star loses lawsuit", The Seattle Times, October 15, 2002. Accessed September 16, 2020. "Josh Fisher, a Mercer Island High School graduate and the 1998-99 state 3A basketball player of the year, has lost a civil suit that claimed his school counselor defamed his reputation and damaged his college basketball career when she passed along rumors that he had cheated on a college-entrance exam."
^Adrian Hanauer, Seattle Sounders FC. Accessed September 16, 2019. "Hanauer’s interest in soccer began at the age of three, and he saw his first NASL Sounders game at the age of eight. He went on to play for Mercer Island High School and remains active in the Greater Seattle Soccer League."
^Bill Hanson, RealGM. Accessed September 16, 2020. "High School: Mercer Island High School [Mercer Island, Washington]"
^Steve Hawes, Basketball-Reference.com. Accessed November 28, 2007.
^Evans, Jayda. "Mercer Island High School retires jersey of Sounders star Jordan Morris", The Seattle Times, April 25, 2019. Accessed September 16, 2019. "Mercer Island’s stadium has been renovated, but the memories of Jordan Morris tearing up the soccer field resurfaced Tuesday. The Sounders FC forward returned to his alma mater to be inducted into its Hall of Fame."
^Celms, Elizabeth. "MI Olympic swimmer still inspires", Mercer Island Reporter, September 9, 2008. Accessed September 16, 2020. "By age 13, Lethcoe was ready for competition. But in 1952, girls’ competitive sports were nearly non-existent. It would be more than 20 years before Mercer Island High School offered a girls’ athletic program, and Eastside youth club sports were dominated by boys."
^via Associated press. Also as of 2014 became the coach of the Utah Jazz (Basketball team) "Missouri coach Quin Snyder resigns", The Seattle Times, February 10, 2006. Accessed May 20, 2008. "Snyder, a graduate of Mercer Island High School, spoke to his team before practice today and said he was leaving."
^"Loyola names Sheryl Swoopes head women's basketball coach", KCBD-TV, April 12, 2013. Accessed December 16, 2020. "Swoopes was an assistant girls basketball coach at Mercer Island High School in 2010 and most recently served as a television analyst for Texas Tech women's basketball games during the 2012-13 season."