Catholic schools reserve around 30% of places for non catholics, these are usually allocated on proximity of the childs home address to the school, so you've got a chance without getting your child baptised, just ask the school for a copy of its admissions policy. If you get your child baptised you will be expected to bring them up in the catholic tradition and if the priest thinks you aren't genuine he's under no obligation to baptise your child (unlike an anglican priest), I don't know the rules but I would imagine if you're not married for example it might make things difficult.
I would say at the end of the day it's a matter for your own conscience, but it is dishonest to have your child baptised into a faith without any intention to raise them in it.