In the United States, a teacher-librarian must have a baccalaureate degree and a certificate in secondary or elementary education, and must also complete a school library media program and gain a state certification. Programs in library science vary between institutions; however, state requirements must be met before a library media specialist is allowed to teach. Some school library media specialists hold the full Masters of Library Science (MLS) or Masters of Library Information Science (MLIS) degree, while others do not.