Education in Serbia is regulated by the Ministry of Education and Science. Education starts in either preschools or elementary schools. Children enroll in elementary schools at the age of seven. Compulsory education consists of eight grades of elementary school. Students have the opportunity to attend gymnasiums and vocational schools for another four years, or to enroll in vocational training for 2 to 3 years. Following the completion of gymnasiums or vocational schools, students have the opportunity to attend university. Elementary and secondary education are also available in languages of recognised minorities in Serbia, where classes are held in Hungarian, Slovak, Albanian, Romanian, Rusyn, Bulgarian as well as Bosnian and Croatian languages. Petnica Science Center is a notable institution for extracurricular science education focusing on gifted students.