Across the Iowa border, in Fremont, Neb., Ashley Sandoval makes $10.50 an hour at another Great Clips location. In the five years since she graduated from cosmetology school , she said, interest has ballooned her debt from $22,000 to $29,000. “I’ll be paying it off for the rest of my life,” Ms. Sandoval said.

The Iowa Cosmetology School Association, which acts on behalf of several of the 13 companies that own schools in the state, would not make a representative available for an interview. But the association did provide written responses to questions through its lobbyist, Threase A. Harms. The group said that its primary concern was successfully preparing students, not making money, and that differences in state regulations made comparing hours difficult. The association also doesn’t see the crippling student debt as the schools’ fault, citing the fact that students are allowed to take out more in loans than is necessary to cover educational expenses. “We have students graduating with minimal debt because they made wise choices,” the association said.

‘A business first, and a school second’

Cosmetology schools have a unique business model in the for-profit school world. They have two main streams of revenue. The first comes from students, often in the form of taxpayer-funded grants and loans to pay for the tuition. Cosmetology schools took in nearly $1.2 billion in federal grants and loans during the 2015-16 school year.

The second stream is the salon work the students do while in school. They spend some time in classrooms learning about, for example, chemicals and how to sanitize the work space, but once they’ve hit a certain number of hours, they start working on real clients in salons run by the schools. In full-time programs, going to school becomes a full-time job, where students clock in and out for seven- or eight-hour shifts.

The total number of required hours varies, but all states require some amount of practice with paying customers. In Iowa, students spend 715 hours in the classroom and 1,385 hours on the floor.

Prices for these salon services — which include haircuts, manicures, facials and, at some schools, massages — are typically set below market rates to attract customers. The salons also sell shampoo, conditioner and other beauty products. One Iowa student said he and others had gotten perks (such as trips and special training) if they sold enough products. Another student, who sued a school in Pennsylvania, reported that her grades were partly based on whether she offered salon products to clients.

The schools don’t have to pay students for the services they provide; in fact, the students pay tuition for the hours they work in the salons.