Get a certified copy of your name change order and forward it to them, stating that they're in violation of the court's ruling if they opt not to update your records and reissue them under the correct name. I had my name legally changed while IN high school in Virginia, and still had to fight my school to get the records changed with my certified order(funny, because my diploma had yet to be made and the orders wouldn't go out for months). It takes a bit of fighting, I find, but if your order is worded correctly, they have to change it.
Back it up with a copy of your ID, etc to help prove that this is your legal name and it's a big deal to have your records amended, especially if they're incorrect. I know a girl whose middle name was changed by her parents without her knowledge in high school, and upon graduating was furious to find a new and unwanted name on her diploma. After amending her name with her state and social security etc, she fought her school until they fixed her records.
In the end, they may still refuse to fix your records and you can make the choice to pursue it with a lawyer or other help. If they do opt to change it following everything, you might have to pay a fee for new records, but at least it'll be in your proper name.
EDIT: To add to my story: I had to go over my principal's head to the superintendent to get them to fix my stuff. You may have to do that as well.