Although I teach middle school and NOT in the area of Math, I am in charge of the after school study room for latch key kids.
I get a lot of primaries needing help with math. All I can say is use manipulatives as much as possible. There are also some online games the kids love to play that works well. If he has a computer I would give him some games for "homework" between sessions.
National Library of Virtual Manipulativesfor Interactive Mathematics
King's List of On-line Math Activities