Compulsory education and school laws were enacted in the British colonies of North America beginning from the 1640s. Compulsory school laws were gradually enacted in all states of the United States of America between 1852 and 1918, with enforcement of the laws following gradually and but unevenly in the various states. Today, most states require attendance up to age 16. Music was gradually introduced to the elementary school curriculum from the 1830s. Today, music is mandatory for all (general) students in Grades 1-6 in most schools and in some schools in Grades 7-8, and is an elective subject in most schools in Grades 7-12. General music classes in the U.S. are similar to compulsory music classes in many other countries. Approximately 25 percent of American public secondary school students participate in elective music performing ensembles, which are a distinctive and positive feature of American music education.