.The public schools will likely not deviate from the Algebra II/Geometry/Pre-calculus/Calculus sequence in grades 8-11.
Have they told you this or is it an assumption? I’d certainly find out for sure before making a decision.
It's based on experiences with my older son. He has been more mathematically precocious than his younger brother, and he is taking precalculus in 10th grade and scheduled to take calculus in 11th grade next year. He has taken calculus at RSM this year and took the AP Calculus BC exam. If he finds out this summer that he got a 5 on the BC Calculus exam, they will move him to online classes in differential equations, multivariable calculus, or linear algebra. So I guess acceleration is possible based on a standardized test score.
When I was in junior high school I took math classes at the high school during first period as part of the gifted program. Few Massachusetts public schools have gifted programs, and block scheduling means that it is impossible to take one class at the high school and the other classes at the middle school, since one school could have a 6-day schedule and the other school a 7-day schedule.