My now-9-year-old MG/HG son was in public brick-and-mortar elementary school for 4K - 1. Each fall he tested beyond grade level. He had 3x week pullout out for reading, but he was with other advanced children. Only he was far more advanced than the others so it was not meeting his needs. The summer before 2nd grade, they offered him 3rd grade math instruction - but they had tested him at mid-way through 4th grade level for math. In sum, the elementary school was not able/willing to meet his needs in spite of their use of advanced cluster classroom, free use of differentiation, normalizing pull-outs for all students for various reasons, and written acceleration policy.
I switched him to the same district's public virtual charter where they were willing to subject acceleration without hassle. They just asked him to read a section from a 4th grade textbook and ordered 4th grade curriculums for him. We stayed with the virtual charter for 2.5 school years. Officially, grades 2, 3, and 7. They did a formal 3 grade skip the last year which allowed him to take high school courses for credit. However, because of budget limitations, they also have a policy that students need to be getting good grades before they can enroll in electives. My son refuses to so easy work, his grades suffer, and he can't take electives. The high school classes were too easy for his tastes, as the virtual school network in my state is geared towards at-risk students.
Now he is homeschooled, heavy music electives, and studying for AP and/or CLEP exams. He wants to enter college early and has taken placement test at the local community college, but I'm holding out until he takes AP or CLEP tests and scores well.
The virtual charter was never a good fit for us, but I'm very thankful for it. At the time, my XDH (shared custody) was completely against homeschooling. The virtual charter school was the best fit within the constraints I was working with. Now my XDH is supportive of homeschooling, so I'm free to do homeschool.