Dozens of public school districts around the state have signed contracts to enroll foreign students in their high schools, attracted by the prospect of thousands of dollars in tuition revenue and a chance to diversify their student bodies.

Recruiting firms, tapping the growing hunger — primarily in China — for an American education, connect students with the schools for a handsome fee.

Districts that work with one such company receive between $9,200 and $16,700 from each family of an international student, according to a Globe review of 21 contracts that districts signed with that company,the Waltham-based Cambridge Institute of International Education. The contracts also reveal that host families receive between $5,000 and $10,000 a year, depending on the district, to house and feed them.

Public schools are the latest frontier for foreign students seeking US diplomas, which they believe will help them gain admittance to US universities. The booming industry of companies that funnel these students into schools has thus far focused on private and Catholic schools. With those markets saturated, the companies have begun zeroing in on public schools as their next lucrative target.

Federal law limits foreign students to one year of study at public schools; there is no such limit for privates. School districts face no restrictions on how they use the revenue from foreign students. Some have funded language programs or hired teachers, while others simply put it toward their bottom line.

“For us, it seemed like a good thing,’’ said Robert Monteiro, superintendent in Swansea, a Southeastern Massachusetts town of about 15,000. “Swansea’s a small town — not a lot of diversity.’’

While the public school market for international students is growing, it is still relatively small. In Massachusetts, 447 international student enrolled in public schools in 2015, compared to 5,517 in private schools, according to the Department of Homeland Security. (In 2010, there were just 97 such students in public schools.)

Companies such as Cambridge Institute are focusing on Massachusetts because the state is known for its high-performing public high schools and top universities. Two years ago, the company hired two former local superintendents to pitch its services to schools from North Andover to Scituate. So far, 23 districts have signed up with the firm and at least an additional 18 work with other recruiting companies.

But districts are learning that dealings with these companies carry risks. Schools that contract with Cambridge Institute rely on the company to vet students, translate transcripts, tutor, and match students with host families. Yet if something goes wrong, it’s the school’s reputation that could suffer.

“Your average school doesn’t fully grasp those risks,’’ said Eddie West, director of international initiatives at the National Association for College Admission Counseling, which closely monitors the international student recruitment phenomenon.

There is little government oversight of this burgeoning industry. The state does not monitor districts’ contracts, nor how they spend the revenue. And while the federal government monitors schools and individual students, it does not scrutinize the companies.

Many superintendents said they are frustrated because Cambridge Institute has not delivered the target number of students specified in their contracts, often because it cannot recruit enough host families. Districts do not have to pay to enter into an agreement and the number of students is a goal, not a requirement, the contracts show.

Former employees of Cambridge Institute suggest the problems go deeper. In interviews with a dozen of them, and in official complaints filed with the Massachusetts Commission Against Discrimination, they told of a computer hack of host family financial information stored in a database and of Chinese students who refused to live with nonwhite families. Employees, in the complaints, said the company is internally chaotic and puts profit ahead of students’ and schools’ well-being.

If that is true, you wouldn’t know it from a visit to the company's Waltham headquarters. Located on the third floor of a nondescript building on Main Street, the office is serene and sparse. The company’s name hints at the dreams of many Chinese parents strive to send their child to an elite US college such as Harvard or the Massachusetts Institute of Technology, both in Cambridge.

Co-owner Christine Lin said students’ well-being is the company’s top priority, and it has a detailed method of responding to concerns.

“I do admit that there’s always room to improve,’’ Lin said. “Especially when we are growing fast and we’re moving mountains, there’s a lot of different perspectives.’’

Cambridge Institute was founded in 2009 by Lin and her husband. As a pioneer in this field, it kept its sales pitch simple in the early days: Struggling private schools could multiply their revenue by trusting the company to fill empty desks with international students who pay full tuition, and sometimes more. Now the company faces competition from other firms that have replicated its business model.

Students who attend public schools pay Cambridge Institute a flat fee, which next school year will be between $29,543 and $39,500, the company said. Part of that sum is then paid to the district and the host family. The amount paid to the district is similar to the cost to educate a local student.

To lead the Massachusetts push, the company hired John E. Phelan, the retired superintendent of Hopkinton, and Bob Maguire, his retired counterpart in Medfield, both of whom had pioneered international student recruitment in their districts.

Many districts say they hope to see more students soon.

“It’s a little bit disappointing when they want you to do a lot of work on this end and then you’re only getting one student,’’ said Swansea’s Monteiro, who signed a contract with Cambridge in 2014 that set a target of five to 10 students per year but so far has had just one per year.

Another issue is that districts often trust recruitment companies to decipher Chinese transcripts, to see that students who seek diplomas meet US requirements. The students, who usually come in their junior or senior year, must pass US history as well as MCAS tests in math, English, and science to graduate.

Districts insist they do not lessen the requirements for foreign students, some of whom arrive with sub-par English skills that require a private tutor or ESL classes.

“I will not weaken the worth of a Holliston High School diploma,’’ said Bradford Jackson, the superintendent of that district, which hosted two students last academic year.

Recruiting host families is also a challenge. In small, suburban towns, it can be hard to persuade a family to open its doors to a stranger, Cambridge Institute officials said.

Former employees said recruitment problems are more complex. Many Chinese families request their children be placed with a white family, the employees said.

“I would constantly hear, ‘Oh, that family’s black,’ ’’ said Rayshauna Gray, who is black herself and worked in the company’s Waltham office for a year in 2013 and 2014.

Lin, the co-owner, said it is working to reverse cultural stereotypes among Chinese families.

“It’s going to take time for us to educate them, to say ‘Hey, America is like this,’’’ Lin said.

Employees, in their complaints, cited a host of concerns with Lin’s operation.

One complaint, submitted last week to the MCAD, alleges inapproprate behavior by a person employed by Lin’s company at a dormitory the company runs at one private school.

Lin, in an interview, declined to discuss the complaint except to say the staffer did nothing wrong and was well-liked. The school, in a statement, said Cambridge Institute investigated the allegations and found that students were never in danger.

However, the company found that the staffer violated its employee code of conduct and no longer works for the company, the school said.

“We believe this matter was handled effectively,’’ the school’s officials said in a statement.

Two other MCAD complaints, filed in 2014 and 2015, were withdrawn in order to be filed as lawsuits in court, according to the commission. All three complaints were filed by employees who had been fired.

Another former Cambridge Institute employee said in an interview that the company stored student health data and financial information about host families in an unprotected database that was recently hacked. The employee said he repeatedly warned executives that information was vulnerable and suggested ways to secure it.

“They just didn’t want to spend the money. Always the cheapest possible way, that’s the way it was going to be done,’’ said the employee, who spoke on condition of anonymity because he still works in the industry.

Cambridge has acknowledged the data breach and hired a consultant to help secure the information, Lin said. It has also revamped its hiring and employee training and recently hired a new team of top executives, she said.

Most districts are hopeful the company will work out its kinks and they will see the diversity, and revenue, they were promised. Others are losing patience.

The Dudley-Charlton district signed contracts with Cambridge Institute the past two years to accept up to five students each year, but none came, said principal Mary A. Pierangeli.

“I expressed my displeasure with their inability to provide us students. They assured me that this would be a better year,’’ Pierangeli said.

Since then, she has not heard from the company. She said she plans to stop working with them.

Laura Krantz can be reached at laura.krantz@globe.com. Follow her on Twitter @laurakrantz.