Many people ask that question.  There is no federal student tax.  This is one of the scams used by IRS impersonators.  They usually threaten criminal prosecution if the student does not immediately wire funds or provide a credit card to them.  There are many similar scams operating at this time.  Remember that the IRS will never call you and demand money over the phone.  Also, they will not threaten you with criminal action by phone.  You (and anyone who gets such a call) should notify the Treasury Inspector General for Tax Administration (TIGTA) and that department will follow up.  Their contact information can be found at www.irs.gov.