Mater Dei Prep: A Catholic Preparatory School (commonly known as "Mater Dei High School") was a four-year Catholic coeducational high school that served students in ninth through twelfth grades, located in the New Monmouth section of Middletown Township, in Monmouth County, in the U.S. state of New Jersey.

History The school was founded in September 1961 by the Reverend Monsignor Robert T. Bulman and is located on a small portion of the parish's campus."OK Site For New Catholic High School", The Daily Register, November 24, 1961. Accessed May 12, 2022, via Newspapers.com. "The Township Committee Wednesday night granted a minor subdivision to St. Marys Catholic Church, New Monmouth, paving the way for the eventual construction of a Catholic high school. By virtue of the subdivision, the parish obtains 20.28 acres of land adjacent to the present elementary school site from the estate of James E. Griggs. In September, the parish started a freshman class at Mater Dei High School." The school attracted students from over 30 parochial, private, and public schools in Monmouth County and Middlesex County. The school maintained an average enrollment of 435 students in grades nine through twelve.

Mater Dei was a part of St. Mary Parish and later operated under the supervision of the Roman Catholic Diocese of Trenton.School Finder, Roman Catholic Diocese of Trenton. Accessed January 21, 2018. The school was accredited by the Middle State Association of Colleges and Schools Commission on Elementary and Secondary SchoolsMater Dei Prep, Middle State Association of Colleges and Schools Commission on Elementary and Secondary Schools. Accessed February 7, 2022. and was a member of the National Catholic Educational Association (NCEA).

The virtual learning program began in 2005 and ended in 2010. Virtual learning classes included all levels, including Advanced Placement, in Math, Foreign Languages (Latin, Italian, and Chinese) as well as History.

In February 2015, the pastor of St. Mary Parish announced that the school would be closing at the end of the 2014-15 school year, in the wake of chronic fiscal deficits.Spahr, Rob. "Mater Dei Prep in Middletown announces it will close in June", NJ Advance Media for NJ.com, February 3, 2015. Accessed February 4, 2015. "Just days after a planned celebration for its 50th anniversary, Mater Dei Prep will reportedly close its doors. Citing a severe, multi-year financial deficit, Father Jeff Kegley - the pastor of St. Mary Parish - announced in a letter to parents on Tuesday that the coed Catholic high school would close in June at the end of its current school year." A few days after the announcement, it was disclosed that the Parish Finance Council had agreed to a two-month extension in order to raise the $1 million needed to remain open.Kegley, Fr. Jeff. "ANNOUNCEMENT/Press Release: Parish announces extension for Mater Dei Prep to raise needed funds." , Mater Dei Prep, February 5, 2015. Accessed February 9, 2015. Through the Seraph's Fund, and efforts by the student body, $1 million was raised in a two-month span and the school was able to open for the 2015-16 school year.Carino, Jerry. "Fundraising to save Mater Dei reaches $1 million goal", Asbury Park Press, March 26, 2015. Accessed May 22, 2023. "It seemed like a distant, almost impossible goal at the time: Raise $1 million in two months to keep Mater Dei Prep open.... Officers of The Seraph's Fund, a 501(c)3 organization spearheading the effort, announced Thursday morning that they had reached $1 million in binding pledges.... Once the $1 million is collected, it will ensure that the school will remain open in the fall."

As of the 2021–22 school year, the school had an enrollment of 223 students and 21.4 classroom teachers (on an FTE basis), for a student–teacher ratio of 10.4:1. The school's student body was 66.4% (148) White, 15.7% (35) Hispanic, 11.7% (26) Black, 4.0% (9) Asian and 2.2% (5) two or more races.School data for Mater Del Prep High School, National Center for Education Statistics. Accessed November 1, 2023.

On May 9, 2022, it was announced that the school would be closing at the end of the school year due to a dramatic decline in enrollment.

The school's building was used in 2023 for principal photography of the 2024 film Mean Girls.Rudensky, Franki. "What to know about Tina Fey's Mean Girls movie musical, which premieres in theaters Friday", PhillyVoice, January 9, 2024. Accessed March 5, 2024. "The project completed filming last April in Middletown, Monmouth County, where Mater Dei High School was transformed into the fictional North Shore High School."

The building was demolished in 2025.. The athletic fields and remaining land are now a public park operated by Middletown.

Athletics The Mater Dei Prep SeraphsMater Dei Prep, New Jersey State Interscholastic Athletic Association. Accessed October 20, 2020. competed in Division B Central of the Shore Conference, an athletic conference comprised of public and private high schools in Monmouth and Ocean counties along the Jersey Shore.Shore Conference Realignment for 2018-2019 and 2019-2020, Shore Conference. Accessed November 15, 2020.Member Schools, Shore Conference. Accessed November 15, 2020. The conference operates under the jurisdiction of the New Jersey State Interscholastic Athletic Association (NJSIAA).League & Conference Officers/Affiliated Schools 2020-2021, New Jersey State Interscholastic Athletic Association. Accessed December 11, 2016. With 212 students in grades 10-12, the school was classified by the NJSIAA for the 2019–20 school year as Non-Public B for most athletic competition purposes, which included schools with an enrollment of 37 to 366 students in that grade range (equivalent to Group I for public schools).NJSIAA General Public School Classifications 2019–2020, New Jersey State Interscholastic Athletic Association. Accessed November 20, 2020. The school was classified by the NJSIAA as Non-Public Group III for football for 2018–2020.NJSIAA Football Public School Classifications 2018–2020, New Jersey State Interscholastic Athletic Association, finalized August 2019. Accessed October 20, 2020.

The school participates as the host school / lead agency for joint cooperative football team with Ranney School. The co-op program operates under an agreement scheduled to expire at the end of the 2023–24 school year.NJSIAA Fall Cooperative Sports Programs, New Jersey State Interscholastic Athletic Association. Accessed December 1, 2020.

The boys track team won the Non-Public Group B spring / outdoor track state championship in 1967, 1973, 1999, 2000, 2006 and 2017-2019. The program has won 10 state titles, which is tied for eighth-most among all schools in New JerseyNJSIAA Boys Spring Track Summary of Group Titles, New Jersey State Interscholastic Athletic Association. Accessed May 1, 2023. In June 2018, the team set numerous school records and took home both a sectional title and their second consecutive Non-Public B group state title.Carino, Jerry. "Track: Mater Dei Prep boys win another state title; wild meet for St. Rose's Antognoli", Asbury Park Press, June 2, 2018. Accessed January 20, 2018. "The Mater Dei Prep boys track team’s performance this weekend was the latter. The Seraphs racked up a whopping 99 points to defend their NJSIAA Non-Public B title at Central Regional High School.... He was motivated by Mater Dei’s second-place finish at February’s indoor Non-Public B meet, when Bishop Eustace nipped the Seraphs for the crown."

The baseball team won the Non-Public B South championship in 1967, 1968 and 1970.Baseball Championship History: 1959–2024, New Jersey State Interscholastic Athletic Association, updated September 2024. Accessed September 1, 2024.

The girls cross country team won the Group I state championship in 1976, 1977, 1987, 1991 and 1992, and won the Non-Public Group B state title in 1982-1985. The nine state championships won by the program are ranked fifth in New Jersey.NJSIAA Girls Cross Country State Group Champions , New Jersey State Interscholastic Athletic Association. Accessed May 1, 2023.

The girls basketball team won the Group I state championship in 1980 (defeating Benedictine Academy in the tournament final) and won the Non-Public Group B title in 1990 (vs. Immaculate Conception High School of Montclair).Girls Basketball Championship History: 1919–2024, New Jersey State Interscholastic Athletic Association, updated March 2024. Accessed September 1, 2024. The team won the 1980 Group I title with a 64-52 win in the finals against Benedictine Academy.McLaughlin, Bill. "Mater Dei wins title in Group I", Asbury Park Press, March 22, 1982. Accessed January 17, 2021, via Newspapers.com. "At the moment when everyone connected with Mater Dei girls basketball was noisily celebrating the school's first state basketball championship, made possible by a 64-52 victory over Benedictine Academy in the NJSIAA Group I championship game, the handful of Seraph seniors on the team were quietly hugging and kissing at center court."

The boys soccer team won the Non-Public Group B state championship in 1981 and 1983, against runner-up Eastern Christian High School both years in the finals of the tournament.NJSIAA History of Boys Soccer, New Jersey State Interscholastic Athletic Association. Accessed May 1, 2023. The 1983 team finished the season with a 16-4 record after defeating Eastern Christian by a score of 3-1 at Mercer County Park in the Parochial B finals.Amsel, Michael. "Mater Dei lands Parochial B title", Asbury Park Press, November 19, 1983. Accessed January 27, 2021, via Newspapers.com. "Mater Dei soccer coach Tony Scorciolla was having trouble finding the right words to express his feeling of joy.... 'Something like this' was Scorciolla's way of describing the NJSIAA Parochial B soccer championship, which his Mater Dei team captured last night with a 3-1 victory over Eastern Christian at Mercer County Park."

The boys' tennis team won the Non-Public B/C state championship in 1981, defeating Oratory Preparatory School in the final match of the tournament.History of Boys' Team Tennis Championship Tournament, New Jersey State Interscholastic Athletic Association. Accessed November 20, 2020.

The girls' spring track team was the Group I state champion in 1981 and won the Non-Public Group B title in 1982, 1983 and 2000.NJSIAA Girls Spring Track Summary of Group Titles, New Jersey State Interscholastic Athletic Association. Accessed May 1, 2023.

The boys' track team won the indoor track state championship in Non-Public Group B in 1981.Boys Winter Track and Field Championship History: 1922-2023, New Jersey State Interscholastic Athletic Association, updated November 2023. Accessed February 1, 2024.

The girls' tennis team won the Non-Public B state championship in 1982, defeating Pope John XXIII Regional High School 5-0 in the tournament final.Girls Tennis Championship History: 1971–2023, New Jersey State Interscholastic Athletic Association, updated November 2023. Accessed September 1, 2024."Mater Dei set stage for Parochial showdown", Asbury Park Press, November 4, 1982. That much was made official at Mercer County Park, West Windsor Township, yesterday when undefeated Red Bank Catholic (21-0) and Mater Del (19-3) swept state honors in Parochial A and B, respectively to set up an all-Shore showdown next week, probably Tuesday at a site and time to be announced. Red Bank Catholic's Caseys blanked Immaculate Heart, 5-0, In Parochial A and Mater Del swept Pope John of Sparta Township, 5-0, in Parochial B."

The boys' cross country running team won the Non-Public Group B state championship in 1984, 1985, 1997, 1999, 2007 and 2017. The program's seven state titles are tied for tenth-most in the state.NJSIAA Boys Cross Country State Group Champions, New Jersey State Interscholastic Athletic Association. Accessed May 1, 2023.