Although some are affiliated with larger organizations, most schools are independently owned and operated, and work off the profit of student tuition and membership fees, test fees, sales of merchandise, and other miscellaneous sources.
The amount of money a school owner makes depends on the number of students enrolled, the price of tuition charged, and other sales as off-set by expenses incurred for running the business. Schools in bigger cities, and wealthier districts tend to make more money, but it also depends on the quality of instruction, and the marketing.