When my ds was in 4th we had talked to the school about doing AoPS pre algebra. They agreed we cold but it all fell through pretty quick. Backup plan was to do it after school at home. DS would do AoPS at home every evening and one night a week we had a tutor (High School Boy) come by for an hour or so to answer questions and work on some solutions with him. It worked wonderful.
DS was subject accelerated 2 grades in math since 1st grade so he took 5th grade math in 3rd so he was out of curriculum in that building. They had wanted him to do a whole grade skip several times but we chose not to. They had a High Ability program but it was really just in name only IMO.
In 5th we switched to a private school for gifted kids where middle school starts in 5th. It was a very good match. You could test into upper level math classes.
So it seemed to me that 4th grade forced our hand.
