That cell phone cost looks awfully high. DH and I each have a phone and pay about $65 a month for the two of them.
Lock up the credit cards. DD should not be able to access them at all. I would be beyond angry to see a $316 charge like that.
I'd consider asking her to earn the money to pay you back for those, along with her share of school clothes. I'd say set a limit for each kid for clothes and let them make up the difference if they want to with their own money.
Cable? It's a want, not a need, so if money's tight cut back or cancel it.
You don't have anything for dining out. Is your food budget $275 including eating out?
You might be able to lower your internet fee. We got a promotional rate for 12 months and pay about $14 for DSL. Try calling your provider and see what they offer, maybe check their web site and those of competitors first so you're armed with some facts.
What about other forms of entertainment? Subscriptions? Household items?
Good luck!
This can be a great site for helpful advice and tips.
edit - looks like you've already spent the $500 on clothes and supplies....so disregard the spending limit suggestion this time around, but it's worth thinking about as other things come up for the kids.