magnet schools are fine, they generally tend to be put up in low income neighborhoods and act as one of the very few social aid programs to these regions, as the local populace often get’s accepted before the more well off outside district children
Magnet schools are not fine ,because they’re still allowed to be selective; they don’t have to take people with disabilities, for instance. Since they can take students based on testing, they’re able to weed out students that come from less well-performing public schools, which tend to be more urban, and more non-white. And because they’re structured around a particular field, they’re able to structure themselves so that they can be maximally beneficial to people that are already well-off.
There’s no reason to not put those same programs within an existing public school system, unless the goal is to make public education less accessible to families that aren’t already well off.