To be fair, it is less about "keeping top kids down" and more about "let's use our very scarce resources helping the bottom kids". Put that way it seems less malicious, and more like probably the right thing to do over all, while still being extremely frustrating if you are, or are the parent of, a 'top kid'. I know that in Seattle, I've been very frustrated with all the talk and promise of our school to provide enrichment to kids like mine who are able to learn quickly and are ready for more advanced learning opportunities, only to discover that it is haphazard, often in name only, and there isn't time or interest in providing more.
But it's not because of some drive for 'equity'. I've talked with teachers (as friends, not in a school setting). They're doing what they can with the resources they have.