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, and carry out, Seal of Biliteracy programs to recognize student proficiency in speaking, reading, and writing in both English and a second language. Further, these programs must allow speakers of any official Native American language to use equivalent proficiency in speaking, reading, and writing in such language in lieu of proficiency in English.