Tax Treaty Benefit for F-1??

I am in F-1 status and had some internship income. But my emplyer said since I ever transfered status from F2--F1 and have never left U.S., I couldn't claim tax treaty benefit ($5000 for student) and my income was taxed for Federal and state tax.

My question is that can I claim the tax treaty benefit when filing tax return?

Thank you very much.