Student Non-Discrimination Act of 2013 - Prohibits public school students from being excluded from participating in, or subject to discrimination under, any federally-assisted educational program on the basis of their actual or perceived sexual orientation or gender identity or that of their associates.

Considers harassment to be a form of discrimination.

Prohibits retaliation against anyone for opposing conduct made unlawful under this Act.

Authorizes federal departments and agencies to enforce these prohibitions by cutting off the educational assistance of recipients found to be violating them.

Allows an aggrieved individual to assert a violation of this Act in a judicial proceeding and recover reasonable attorney's fees should they prevail.

Authorizes the Attorney General to institute a civil action in any appropriate U.S. district court for a violation of this Act.

Deems a state's receipt of federal educational assistance for a program to constitute a waiver of sovereign immunity for conduct prohibited under this Act regarding such program.