How do I establish student agency with my top maths kids?

I have been mulling over this question for sometime as I have two students in my class who are currently operating at Stage 7 for maths.  Their number work and the majority of their knowledge foundation  is solid and I wonder if they were to take ownership of their learning in maths this would enable them to identify their own areas of need and their own next steps with a view to deciding the direction of their learning. Thus creating student agency for these particular students..