My ds is at a very academic comprehensive school in year 7 and scoring an average of 90% in maths tests. He has always, without support from home such as practicing or tutoring, scored above 95% in year 6 and was working beyond since reception. He missed out on some algebra lessons (10 days self isolation) but feels he has the hang of it now. However, on the whole he is less easily high achieving in maths, his all time favourite topic than he was at primary.
He doesn't want a tutor as he hates to be instructed and wants to figure it out himself. What support materials can I give him so he can help himself? Are there any good websites or online resources that could solidify what he is learning in secondary school?
They haven't streamed year7 yet but will in the summer term. His teacher says that if he continues to score 90% on average he'll be in the top set. he did this without revising 
What can we do to support him achieve his best? He really is a capable mathematician but I worry a bit that he will fall behind if he thunks he can remain in op set with minimal study.