In the Marianist tradition, many students join
sodality groups to mutually reinforce their Catholic faith. The groups meet weekly and participate in various religious activities. The school also operates Emmanuel, a Marianist
Retreat House devoted to students' spiritual formation. A major co-curricular focus is music. Activities in this area include Band (four levels), Chorus (four levels), Guitar Club, Jazz Band, the Firebird Swing Jazz Choir, Orchestra, Pit Band, and Jubilee Choir, Gregorian Consortium (sometimes called St. Greg's). Publications include
Blue and Gold (a yearbook),
The Renaissance (a literary magazine),
The Phoenix (a newspaper), and the
Blue Blazer Newsletter (a digital newspaper). Kellenberg also has an Academic Quiz Bowl team and a
Science Olympiad team. The Academic Quiz Bowl team came in 11th place at the 2008 NAQT High School National Championship, and placed second in the 2010 season of the New York area TV show
The Challenge. The team won the 2009 New York State NAQT tournament, placing first in the state with the JV team in fifth; at the state level, three of the top five players came from Kellenberg teams. The Science Olympiad team has qualified for the New York State Science Olympiad Competition several times in recent years. A major activity for female students at Kellenberg is the annual Blue and Gold show. Students who participate are divided into two teams, a blue team and a gold team. The girls practice from February until May. The competition takes place on one night in May, and attracts a widespread Long Island audience. In 2006, the school received national attention when the principal, Kenneth Hoagland, canceled the Senior Prom. In a letter from late March 2006, he cited "booze cruises" sponsored by parents, cocktail parties, and the film
American Pie as examples of "adolescent culture being formed and led by the media". The school received national attention from
ABC,
CNN,
Fox News,
MTV,
The New York Times, and
Comedy Central's
The Colbert Report. In 2018, the school reestablished the varsity ice hockey program, as well as established a varsity crew program for both boys and girls. In 2019, a junior varsity ice hockey team was added. ==Notable alumni==