Wow! I'd be furious! Not everyone has the luxury of getting their child to school early or letting them stay late either. This rule makes ZERO sense! Did they give you a reason for it? The only thing I can think is that the work isn't getting done at home (amazing how many parents really don't care that their kids do what they are supposed to), but if that was the case they should make them stay/go early when they show up without any work done. I hope you can reason with them - good luck!