When the principal of Serra High School was hired in 2014, the San Diego Unified School District said Vincent Mays had received his Doctorate at Stamford Hill University. According to Mays’ resume found online, his Ph.D. is in Administration and Supervision.

But three teachers who are also union leaders at Serra High School question the legitimacy of Mays’ doctoral degree. They filed a complaint last week with the District’s Office of Quality Assurance asking the District to look into the matter.

In the complaint, they say Stamford Hill University does not have a faculty and it doesn't offer classes, and is a known diploma mill.

“The Code of Ethics for the teaching profession states you cannot misrepresent your professional qualifications,” Ralf Uebel said.

“We really did not want to believe that potentially this is not a real degree. We looked at academic data bases, we looked at any person employed by Stamford as a researcher, and we didn’t find anything.” teacher Peter Oskin said.

Oskin says even if the school had closed, there would be evidence of its existence.

NBC 7 did find a Stamford Hill University website, and we searched records in Florida, where the website says the school is based. The Florida Department of Education says that university is not licensed and never has been.

The department is preparing to issue a cease and desist order for the university's website. A search of the state’s business licensing website found no records, past or present. A search of the U.S. Department of Education website also showed no records.

NBC 7 also searched online claims that Stamford Hill University could be based in the United Kingdom. A spokesperson from the U.K’s Higher Education Governance, told NBC 7, a university with the name Stamford Hill has never existed.

“If the Ph.D. does not exist, that constitutes academic fraud and we’re in the business of education. We’re trying to teach our students the value and importance of education,” Uebel said.

Since last week, NBC 7 has been asking Mays and the district for comment. The district says Mays will not talk about this, because he feels it is the doing of disgruntled employees.

The district issued this statement: "These vicious personal attacks on Dr. Vincent Mays are shameful. He has devoted his life and professional career to the service of children, including more than a quarter century as a classroom teacher and an administrator. He has every necessary certification and more importantly the skills necessary to lead Serra High School. He has and will continue to have the full support of the district."

Mays earns a salary of $143, 612.64, according to the school district.

“We are not disgruntled. We are looking out for the students,” Nicholas Cincotta said, a teacher at Sierra High School.