How to challenge a grade 7-8 in Maths?

Hi all. My son is in grade 7, going into High School next year. He does well academically, interested in science, tech, robotics, maths. Today he mentioned that school maths is really boring and wants more challenging.

What you recommend online or in-person (Cape Town)? All I can think of is Khan Academy or brilliant.org (never used those but just came top of mind).

Thank you