"Give me the child until he is seven and I will show you the man" is an old Jesuit saying, the Jesuits being an order of the Roman Catholic priesthood often involved in teaching. (Sometimes it is presented as "the child at seven", which puts rather a different slant on the matter.) The basic idea remains the same...if you totally control a young person from an early age, you can almost certainly dictate how he/she will turn out as an adult.
markdona1's version is a parody of the Jesuit saying, not an old religious saying at all. Actually it might not true. I read something that when you get to about fifty your personality comes more from being an adult than a developing child.