Every student needs and should be entitled to an education that pushes their abilities. Without it, they won't learn to put in the effort required to be successful even at a level that doesn't make use of their enhanced abilities.

This might mean that there are additional costs for 'gifted' students. But that's no different than there being additional costs for mentally less advanced students: no matter what the students are, providing an education fit to their needs has costs... and a failure to provide it creates inequality when the most privileged families move their children (or relocate entirely) to places that will provide a more suitable education.