Most schools follow the tradition of school shifts (originally done for lack of space, but now tradition). Thus, school starts for some groups (usually years I to IV and VIII) at 7:30 or 8:00 and ends at 12:00–14:30, while other groups (years V–VII) start at 11:00–13:30 and end at 17:00–19:30. Normally, a class lasts 50 minutes, followed by a 10-minute break (and sometimes one 20-minute break). From November until March, some schools reduce classes to 45 minutes and breaks to 5 minutes, for fear that 6:30 or 7:30 in the evening is a too late and a too dangerous hour to leave school during the dark. School days are Monday to Friday.