About 1,000 teachers in D.C. Public Schools — a quarter of the educator workforce — lack certification the city requires to lead a classroom, according to District education leaders.

The Office of the State Superintendent of Education, which handles teacher certification, said it made the discovery during an internal investigation this winter.

The District’s teachers all have college degrees and have undergone criminal background checks and drug tests, city officials said. The interim chancellor of D.C. Public Schools, Amanda Alexander, said in an interview earlier this week that the lack of city-issued certification does not mean the teachers are unqualified to educate children.

Because of the findings, the school system will require all teachers to start the application process for credentials by the start of the academic year — a strict time frame that hasn’t been mandated in the past, according to Alexander.

D.C. law exempts teachers who work in charter schools from being certified. Nearly half of the city’s children attend charter schools.

“We do believe in the value of licensure,” Alexander said. “Licensure is just one of many components when we look at whether our teachers are meeting a high standard of excellence. Before they receive an offer, we do a background check. Our selection process is rigorous.”

To be certified, teachers must complete exams offered by the District and enroll in certification courses. Educators can be exempt from the certification course work if they receive “effective” ratings on their classroom evaluations. The certification expires after four years, and Alexander said some of the 1,000 teachers hold licenses that have lapsed.

The findings regarding the teachers come against a backdrop of other scandals in the District’s school system involving graduation rates and students from outside the city fraudulently enrolled at an elite arts school.

“I am again frustrated with D.C. Public Schools over this most recent failure to properly follow established laws and regulations,” Council member David Grosso (I-At Large), who chairs the education committee, said in a statement Thursday. “These licensing requirements were put in place to ensure that our students are safe and that we have quality educators in our schools.”

Educator certification is proof that someone has the training and skills to teach according to requirements specified by a school district. It is usually awarded by a state government agency and is known variously as a teaching certificate, teaching license or teaching credential.

Laura Fuchs, a social studies teacher at Woodson High, said she suspects that some teachers who lack the proper credentials simply missed the deadlines to renew them.

She said that there is typically only a small window of time to renew and that the deadlines can be confusing. Her credentials lapsed in January, and she said she was given two dates to file her renewal paperwork. Fuchs was rated as an “effective” teacher for multiple years, so was not required to take courses for renewal.

“We can certainly discuss the standards of what it takes to get a license. But we are a profession, and we should be trained as educators,” Fuchs said. “Parents have a right to know that we are trained.”

When President Barack Obama signed the federal Every Student Succeeds Act into law in December 2015, it abolished federal certification requirements, leaving it up to the states to decide whether and how to certify teachers. Supporters of stringent licensing say schools that hire teachers without certification are devaluing the profession, but critics say that a teacher doesn’t have to be certified to be effective. Obtaining the licenses often entails enrolling in training courses.

In recent years, there has been a trend in some parts of the country to allow educators without certification to teach, spurred by severe teacher shortages in many districts. In Arizona in 2017, the legislature passed a law allowing teachers to be hired with no formal teaching training as long as they have five years of experience in fields relevant to the subject they are teaching.

WRC-TV first reported the existence of the D.C. teachers without certification Thursday.

In March 2016, the D.C. superintendent’s office instituted regulations that allowed multiple pathways for teachers to obtain their credentials, which is intended to allow the traditional public school system to better compete with the charter sector for teachers, city documents show.

The superintendent’s office lets newly hired D.C. teachers obtain an initial teaching credential — essentially a temporary license.

To get that license, teachers must pass two city teaching skills exams, known as Praxis tests. The provisional credentials are valid for three years. Alexander said the 1,000 teachers lacking proper credentials do not possess temporary licenses.

Experienced teachers from other jurisdictions also must complete these exams.

Chloe Woodward-Magrane, spokeswoman for the Office of the State Superintendent of Education, said the agency is working with the school system to ensure it complies with the certification regulations.

Thomas Blair Jr. said he has been satisfied with his granddaughter’s teachers at Savoy Elementary in Southeast Washington but is concerned that so many teachers lack credentials — particularly when he assumed they had them.

“It’s alarming that they would be able to teach when they don’t have the certification,” Blair said. “My understanding was that they had to be certified to be a teacher.”

Alexander said the school system has it own development programs — which do not lead to credentials — to improve teachers in the classrooms. She highlighted LEAP, an in-house program that has instructional coaches and weekly seminars to help make teachers effective in the classroom.

The school system works with Urban Teachers, a training program in collaboration with Johns Hopkins University’s School of Education, to bring educators with the proper certifications into D.C. classrooms. Those in that program, who spend three years teaching under a temporary license, graduate with a master’s degree.

The District also works with programs that are less intensive to certify teachers.

Jacqueline Greer, executive director of Urban Teachers D.C., said educators in the program learn how to lead a classroom and about different teaching strategies.

“We designed a program that ensures that they are going to be effective before they enter the classroom,” Greer said. “We want to prepare a teacher like we train an emergency room doctor so that they have all the tools to be in an urban classroom.”

Valerie Strauss contributed to this report.