ALTER TABLE schools ADD COLUMN start_time TIME NULL;
ALTER TABLE schools ADD COLUMN lesson_duration INT NULL DEFAULT 45;
ALTER TABLE schools ADD COLUMN short_break INT NULL DEFAULT 5;
ALTER TABLE schools ADD COLUMN long_break INT NULL DEFAULT 20;
ALTER TABLE schools ADD COLUMN long_break_after INT NULL DEFAULT 2;
ALTER TABLE schools ADD COLUMN total_lessons INT NULL DEFAULT 7;

UPDATE schools
SET start_time = COALESCE(start_time, '07:45:00'),
    lesson_duration = COALESCE(lesson_duration, 45),
    short_break = COALESCE(short_break, 5),
    long_break = COALESCE(long_break, 20),
    long_break_after = COALESCE(long_break_after, 2),
    total_lessons = COALESCE(total_lessons, 7);
