Beacon Community College, Crowborough, beat Hove Park 21-12 in the opening round of the Daily Mail Under-18 Schools Cup.
They led 6-5 at the interval through two penalties by fly-half Sam Denereaz, wing Keeba Edwards scoring a try in reply.
Tom Carruthers put Beacon further ahead with a try converted by Denereaz.
Hove replied with a converted try from Tom Smith before Denereaz scored an unconverted touchdown.
Tries from Kevin Danagher-Smith, Max McAlistair and Andrew Keelaghan, plus two Sam Middlehurst conversions, eased Worth (Crawley) into the second round as they beat Cardinal Newman (Hove) 19-3.
Brighton Hove and Sixth Form College lost 44-0 against Lewes Tertiary College. John Reed and Jim Prescott both ran in twice.
Christ's Hospital (Horsham) overcame Collyers Sixth Form College 15-10. Alex Woodbridge scored tries converted.
Even All-England under-15 100m champion Wade Bennett-Jackson, who scored four tries, could not stop Worthing High losing 37-24 to Christ's Hospital in the under-15s' competition.
They are at Worth who beat Cardinal Newman 17-12.
Eastbourne College beat Bognor Regis Community College 50-0 James Grey ran in three tries.
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