Hmm. Can't speak about your specific magnet program. My child has been in one 1-5th grade (not a gifted magnet) and will be in one 6-12th grade (also not a gifted magnet). So twice I have chosen magnet over zoned school. My son is pretty resilient and makes friends quickly. He left his zoned school afte preK and K and didn't look back. It helps that the magnet programs for us are still within 2 to 3 miles from our house so going to play with friends was still quite easy (both old friends and new friends).

What I have done with the major educational decisions for him (including a grade skip away from a beloved best friend) is to ask myself the following questions

1. Is what he has working?
2. Is what I am looking at a bit better?
3. Will staying harm him in the long term?
4. Will switching gears take some work and feel uncomfortable in some ways and is that such a bad thing?
5. Knowing him as only his parents know him, what is my gut saying (about the education part of it, we can figure out the other issues as they arise or not).

I wouldn't change any decision or change for him so far. I would like to change some of my inaction (looking at you kindergarten year). But he appears to have survived that despite my inaction.