Education Here Needs a Good Bra

As in good support. I have had it with everything being the school's dilemma. Case in point: This week I had an out of school suspension guy with longish hair. It wouldn't have been an issue at most schools, but our dress code is that no one can have hair in his or her face. So the first day I gave him two of my own bobby pins so he could fix it, and told him to come back the next day with it out of his face. He didn't, so he had laps for violation of dress code. Another teacher told him that a high school boy had come in like that and had it cut at school. She never said that he had to do the same; she just shared that little tidbit.
The next day his mother wrote something on the daily report to the effect of, "I don't see why he has to cut his hair when he's only there for five days."
So I wrote, "He doesn't need to get it cut; he needs to find a way to keep it out of his face all day. Bobby pins or hair gel would be fine."
Her response? "Gimme a break!"
I shit you not. She even spelled it like that. I cannot express to you how very badly I wanted to staple a Kitkat to his daily. But I fought the urge and didn't write a response. You just can't argue sometimes and accomplish anything.

My point is this: How can we convince the kids it's important to follow rules if their parents so clearly don't give a shit? How can we change a child's behavior, work ethic, or attitude when we often get them in their teen years and only see them from 8-3ish? Some of our parents are stellar at backing us up and setting goals and limits with their kids, but then we get some like this guy's and it really depresses me.