Trying to limit 'screen time'

Here is the system we are using to try and limit 'screen' time with my 8 year old.  I created this chart for the fridge.

We were having trouble keeping track of time on a clock so I went with time slots where he has time to choose his activity.  He is responsible to sign up for time slots. He can only choose screens for 3 of the time slots. He MUST pick 2 of 3 of the following, homework, playing outside, and reading.

I should tell you that my husband and I both teach at the school our son goes to so he 'hangs out' with us before and after school.  That accounts for the time slots that are 'in dad's office' and 'extra waiting at school' (when we have meetings or practice after school).

This is a work in progress.

Today he signed up for a time slot at school and he forgot his DS.  I told him that it was his responsibility and if he didn't have his DS then he didn't get to play.

Click here for my chart