Shea, a 1973 alumnus of the school, posted a 32-23 record in his five years at the helm. Shea finished his career with three straight winning seasons and a Class LL championship game appearance in 2013.
He will remain on the coaching staff going forward, and will continue to teach English at Prep.
Hellstern, a social studies teacher at Prep, has been the team's defensive coordinator since 2013. He coached on numerous college and high school coaching staffs, including Amherst College, Columbia University, Wesleyan University, The Hotchkiss School, The Dwight School and Poly Prep Country Day School.
A native of Glen Ridge, N.J., he played in college at Wesleyan University as an offensive and defensive lineman.
Prep finished 7-4 in 2014. The team made significant improvements under Shea, who took over a team that went 0-10 in 2009.
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