Our rule is no screens of any kind until school is done and after lunch. The "after lunch" part is because their behavior deteriorates horribly the rest of the day if they watch in the mornings. Don't know why, but it is our reality. We watch 1-1.5 hours per day when we watch. I read
Reset Your Child's Brain, and it was quite enlightening. Simply watching a screen from across a room has far less of an effect on the brain (though still an effect!), than screens you interact with and/or are closer to. So I allow basically zero computer, video games, iPad use, smart phone use, etc right now. Eventually we will have to introduce those things and work through how to not abuse them (we have both psychiatric and addiction issues in our family history on both sides), but in the meantime, I want to set them up for success since they are still so young (ages almost 4 to 8.5).
We don't watch anything on weekends, and sometimes, like this week, we have a screen-free week just to focus on playing and doing other things outside.