Here is my experiences with a highly rated public school system. It actually took quite a bit for us to actually leave. We tried very hard to make it work.

The public school did not meet the academic needs of HG child, even with much parent advocacy. It's not that they didn't do anything, but did not do nearly enough.

They value fitting in.

The teachers in charge of the gifted programming were very overworked.

Classroom teachers were overwhelmed with other responsibilities and when they prioritized, they put gifted students last. Some teachers were just did not have enough training on gifted education.

The public school admins and some teachers discount parent input about their children.

The public school allowed bullying as par for the course and then blame the victim instead of addressing it.

Structure of public school taking away recess and adding busywork and extra homework that parents do not agree with.