Extra math classes for a fourth grader

Hi-

My friend has a fourth grader who is currently at a school where they are getting limited math classes. My friend is concerned that her son will begin to struggle in math because he is not being taught enough online instruction. I am wondering if anyone has any recommendations for supplemental math classes for a fourth grader or virtual math summer camps so that he can be sure to be practicing his math. Any suggestions would be greatly appreciated.

Thank you,

-E