They exist. I was quite poor while my first 2 kids were in high school. Oldest got a scholarship to a private school, second went to a magnet ‘school within a school’ and both were admitted based on test scores and essays. Second 2 kids, one went to the school within a school academic magnet and the other to a performing arts magnet school.

So not “gifted” per se - that’s the testing you have to put them through to get them in good public school classes in regular schools in grade 1-8, testing for potential, basically. Magnet school for those grades is allegedly random choice but you are correct it’s not all that random, it’s weighted. For high school it’s by achievement not potential.