Exactly. There are involved parents whose kids are going to thrive in the public school. There are uninvolved parents whose kids are going to do poorly no matter where they are.
So the question becomes "should more taxes be spent to disproportionately favours kids whose parents are uninvolved, in the hopes that they reach the same outcome as kids of the involved parents?"
If a school system is organized around providing each child with the same investment of education and expecting some to make use of that investment more than others, then answer would be no. If it is organized around trying to get the same outcome from each child regardless of how much it costs, the answer is yes.