Just send them to our local school. You can get an “A” and still not stay in the advanced level courses, because the union says the teacher gets paid more and can only have 17 students per advanced class, so the favorites with an “A” get to take certain classes but are no smarter.
With grade inflation, wouldn’t a majority of a kids end up in ‘gifted’ classes by your criterion?
(That’s not saying there’s not unfair favoritism at your and others’ schools.)