Students have about 30–40 periods of 45 minutes each per week (depending on year and state), but especially secondary schools today switch to 90 minutes lessons ("Block") which count as two 'traditional' lessons. To manage classes that are taught three or five lessons per week there are two common ways. At some schools teaching 90 minutes periods there is still one 45-minute lesson each day, mostly between the first two blocks; at other schools those subjects are taught in weekly or termly rotations. There are about 12 compulsory subjects: up to three foreign languages (the first one is often already taken in primary school, the second one beginning in 6th or 7th grade, another is taken somewhen between 7th and 11th grade), physics, biology, chemistry, civics/social/political studies, history, geography (starting between 5th and 7th grade), mathematics, music, visual arts, German, PE and religious education/ethics (to be taken from primary school on). The range of offered afternoon activities is different from school to school however, most German schools offer choirs or orchestras, sometimes sports, theater or languages. Many of these are offered as semi-scholastic AG's ("Arbeitsgemeinschaften" – literally "working groups"), which are mentioned, but not officially graded in students' reports. Other common extracurricular activities are organized as private clubs, which are very popular in Germany.