I don't think it's possible unless your child is exceptionally bright. A lot of parents will not willingly withdraw their child from this school. You can try but don't put your hope too high.
I have two sons studying n St. Jo, one is P5 and one is P1. I haven't heard that there were new classmates coming. I only heard that someone were leaving the school. I have friends, whose boys were St. Jo boys, their boys quit the school because they could not adapt the school's culture.