My son skipped 2nd grade math. The district officially grade-accelerated him in math at the end of first grade. Our elementaries are K-5. In 5th grade I dropped him off at a middle school in the morning. He took math 1st period then they bussed him to his elementary school.

He took high school algebra during his 8th grade year.

In retrospect I probably wouldn't do it again. In 5th grade he resented going to school an hour longer than his classmates. He developed a very bad attitude about math that year that may or may not have happened if he stayed on his regular grade level course.

I wish his second grade math teacher just found ways to extend the curriculum for him instead of skipping the whole year.

I don't think he missed foundational skills. As a little guy he had quite a mathematical mind. In kindergarten he figured out the concept of multiplication on his own and I remember him at 5 discovering that 2 is the only even prime number.

Now he hates math.