Biliteracy Education Seal and Teaching Act or the BEST Act - Directs the Secretary of Education to award renewable two-year grants to states to establish or improve a Seal of Biliteracy program to recognize student proficiency in speaking, reading, and writing in both English and a second language.

Requires students who wish to participate in such a program to submit an application to their state that includes assurances that they: (1) will receive a secondary school diploma or its equivalent in the year they apply; and (2) have met the state's criteria for demonstrating proficiency in speaking, reading, and writing in both English and a second language.

Requires states to provide participating students who demonstrate that proficiency: (1) a permanent seal or other marker on their secondary school diploma or its equivalent, and (2) documentation of that proficiency on their official academic transcript.

Allows students who gain proficiency in a second language outside of school to participate in such programs.

Prohibits states from charging students an application fee.