Biliteracy Education Seal and Teaching Act or the BEST Act This bill directs the Department of Education to award renewable two-year grants to states to establish or improve Seal of Biliteracy programs to recognize student proficiency in speaking, reading, and writing in both English and a second language. States must provide to participating students who demonstrate such proficiency: (1) documentation of that proficiency on their official academic transcripts, and (2) a permanent seal or other marker on their secondary school diplomas. Students who gain proficiency in a second language outside of school may participate in such programs. States may not charge students a program application fee.