Ireland caused an early shock at the IRB Junior World Championship by beating Australia by 19-15 in Brittany on Wednesday.
Leinster centre Tom Daly's penalty in the third minute gave Ireland a lead they never surrendered in Vannes.
Ulster wing Rory Scholes scored Ireland's only try after 26 minutes.
Daly landed a difficult conversion as Ireland led by 10-8 at the break and he added a further three penalties in the second half for Mike Ruddock's team.
Ireland will play Fiji on Sunday and then New Zealand on Thursday 13 June.
Ireland: R Scannell (Munster); A Byrne (Leinster), T Farrell (Leinster), T Daly (Leinster), R Scholes (Ulster); S Crosbie (Leinster), L McGrath (Leinster); P Dooley (Leinster), G McGuigan (Exile), A Boland (Connacht); P Timmins (Leinster), J Donnan (Ulster); C Joyce (Ulster), J van der Flier (Leinster), R Murphy (Ulster).