If you are seeking just math tutoring, consider Mathnasium instead. It's a national chain of centers and they do ONLY math. And unlike Kumon, which sends home loads of worksheets the child must do outside the tutoring center, Mathnasium sends nothing home at all -- the child does the work right there with the tutors present to check the work and explain things on the spot. My daughter is in her fourth summer of Mathnasium and enjoys it. Be aware that Mathnasium is not totally private tutoring -- the student goes, does worksheets alongside other kids (but each child is working on his or her own thing) and the tutors circulate among the kids, checking and explaining. It is a much better use of time and your money than paying a tutor a bundle to sit there doing nothing while a child does worksheets; the tutors are always working with someone, yet always have time to explain things to each child.
The other thing we love about Mathnasium is that while they do ask you to set the times you'll be coming in each week, they are very flexible. We only use it in the summers, and our local Mathnasium is great about letting my child come in whenever it's convenient, even if it's not the times we specified. They understand that kids' summer schedules change from week to week as kids go to different camps and activities.
We have not done Kumon but know several families who have, and they say it is a ton of work at home -- mostly a worksheet factory that expects parents to oversee kids doing a lot of things in their own time.