Very similar here. Additionally I've got 2 kids 13 and 10, both have ipod/phones that have no wifi access before 8am and after 9pm (router schedule against mac addresses).
I remember when I had similar restrictions imposed on me when I was staying with another family during term time. Personally I hated it, I used to secretly alter the settings so that my time was extended because I didn't like being forced off. Eventually they gave up with the restrictions and I went back to using the internet less, I guess I just wanted it more when I was told I couldn't have it. Not saying its the same for your kids but it just reminded me of my internet rebellion!