My son residence is in Fl and working in nyc. We are claiming him as a full time student this year but he has had ny and nyc taxes withheld. He also worked in Fl over the summer. How do I file this?

Evidently, your son lived in NYC.
Any income earned while in NY must be reported to NY. He will file part year resident return. Your U.S. Tax Return: Working or Living in Two or More states