Personal anecdote: I started in private school for K-3, and then public school for 4-12. Public school was remedial until AP Calculus BC in high school. I was skipped in 6th grade to advanced 7th grade math but was harassed by the teacher who also encouraged the class to harass me as well.

I say nudge and try to introduce concepts with Kahn Academy videos and then do problems in between. See how far they can go because kids tend to learn faster than we give them credit for. Keep it fun because keeping curiosity alive is precious.