End Radon in Schools Act - Directs the Administrator of the Environmental Protection Agency (EPA) to review, update, revise, and publish the Radon Measurements In Schools Guidelines with current information and guidance on radon testing in public elementary and secondary schools.

Directs the Administrator, subject to the availability of appropriations, to award grants to states to: (1) follow the updated Guidelines, (2) test radon levels in their public elementary and secondary schools, and (3) provide funds to their local educational agencies (LEAs) to mitigate and re-test radon levels in schools found to have radon levels that the updated Guidelines deem unsafe.

Requires the Administrator to conduct such mitigation directly or by contract if an LEA does not certify to its state that it will use grant funds to mitigate unsafe radon levels at its schools.

Gives highest grant priority to states whose total landmass lies in Radon Zone 1 and second highest priority to states with at least 50% of their landmass in Radon Zone 1. Defines "Radon Zone 1" as areas that have a predicted average indoor radon screening level greater than four picocuries per liter.