Similar situation in my family. I have paid taxes in NC since 1988, son was born in 1991 and has paid Fed/NC taxes on both type of tax returns, yet Pitt Community College billed me $3600 out of state since I was working overseas for the US Dept of State.... We should have paid $900 for one half year tuition. Never was able even with all the tax returns to get my money back from these bastards in NC.
As I said, I got lucky, but I was still outraged by having to collect all those documents to prove I was a resident when an illegal who goes to high school for 3 years gets automatic in state tuition.
Did you attempt legal action?