The duration of the module is purely a matter for decision, ordinarily made by thefaculty of the school at the time a modular schedule is introduced. Fifteen-minute mod-ules are common. A school day based on fifteen-minute modules would encompass ap-proximately twenty-five modules. Schools which follow the Stanford School SchedulingSystem use modules of twenty-two minutes; twenty modules make up the day. The Indi-ana Flexible Schedule uses fifteen modules per day of thirty minutes each. RidgewoodHigh School, Norridge-Harwood Heights, Illinois (as one example) has a school day madeup of twenty modules of twenty minutes plus an additional ten-minute module for home・room period.63