The bell schedule is based on a system revolving around the lunch periods. Since each grade eats lunch at different times, periods 4, 5, 6, 7, and 8 are either 30 minutes or 18 minutes long. Two pairs of these period names are attached every day to make a single period, such as "Period 4/5", "Period 5/6", or "Period 7/8". This changes for different grades, i.e. in 6th grade, a period might be called 5/6, and in 7th grade, a period might be called 4/5.