Maybe to lower the chances of other children against your own (wealthy) offspring? So from a very selfish individualistic perspective there is sense? I suspect that might be the base motivation, even though you likely won't find many openly stating that or even are aware of it.
> Maybe to lower the chances of other children against your own (wealthy) offspring?
Some may think and behave along these lines. Their problem is that they conceive economic activity as zero-sum, which it is not.
Good educational outcomes generate wealth for everyone.
For children from much poorer backgrounds it's more likely that making their prospects even worse will just create later negative impacts on society, such as crime, drug addiction, prostitution, gang violence and so on.