The visitors extended their lead after 34 minutes with a try from full-back Jacob Stockdale which Lyttle failed to convert.
Number 8 Kelvin Browne got over the line for Munster on the stroke of half-time converted by out-half Bill Johnston which closed the gap to 7-11 at the break.
An impressive try from winger Calvin Nash ten minutes into the second half brought Munster to a 12-11 lead however a Lyttle penalty on the 56th minute gave Ulster back a two point advantage.
On the 65th minute out-half Conor Kelly got over the line for the visitor's second try which saw Lyttle's conversion drift to the right and wide bringing the final score 19-12 in favour of Ulster.
Munster U18 Schools: Alan McMahon (Rockwell Colege); Calvin Nash (Crescent College Comp.), Paul Kiernan (Captain) (PBC), Dave O'Mahony (Ard Scoil Rís); Willie Coffey (Rockwell College); Bill Johnston (Rockwell College), John Poland (PBC); Joe Ring (PBC), Shane Fenton (Ard Scoil Rís), Shane O'Hanlon (CBC); Cian Barry (CBC), Sean O'Connor (Rockwell College); Ronan Murphy (Castletroy College), Sean Fitzgerald (Crescent College Comp.), Kelvin Browne (Ard Scoil Rís). Replacement: Vincent O'Brien (CBC), Peter Meyer (St. Munchin's College), Colm Fitzgerald (CBC), Evan Mintern (CBC), Tommy Anglim (Rockwell College), Rory Cunningham (Castletroy College), Michael Clune (CBC), Gary O'Sullivan (Crescent College).
Ulster U18 Schools: Jacob Stockdale (Wallace HS); Robert Lyttle (RBAI), Zach Bertenshaw (Sullivan Upper School), Andrew Magrath (Ballymena Academy), Matthew Butler (Campbell College); Conor Kelly (Methodist College), Cameron Fulton (Coleraine AI); Conor McIlmurrray (Campbell College), Andrew Shaw (Capt.) (Bangor GS), Elliott Boyd (Campbell College); Harry Cleland (RBAI), Conal Murphy (Rainey ES); Conall Boomer (Methodist College), Jonny McKeown (Ballymena Academy), Josh McIlroy (Ballymena Academy). Replacements: Ben Pentland (Wallace HS), Peter Cooper, (Sullivan Upper School), John Clarke (Portora RS), James Houston (Sullivan Upper School), Aaron Haigh (Campbell College), Cameron Stewart (Campbell College), Mark Adair (Sullivan Upper School),Jordan Hylton (BRA)
Referee: Nigel Correll