By Nick Valencia, CNN

(CNN) -- The Department of Education's Office for Civil Rights has launched an investigation into an Atlanta public elementary school after allegations the principal was assigning Black students to certain classes.

In the letter provided to CNN, the Office for Civil Rights said it will investigate allegations of discrimination based on race and whether Atlanta Public Schools subjected students at the school "to different treatment based on race." It will also look into whether the district retaliated against the complainant.

The Office for Civil Rights launched its investigation November 14, according to a letter sent from the Department of Education to Atlanta Public Schools. The inquiry by the federal government comes more than a year after a Black mother filed a civil rights complaint with the office saying her children's elementary school placed Black students in separate classrooms from their peers based on their race.

In a September 2021 interview with CNN, parent Kila Posey, who has two children at Mary Lin Elementary School, alleged that during the 2020-2021 school year, Principal Sharyn Briscoe designated two second grade classes for Black students without the consent of families, while White students were able to be placed among all six second grade classes.

Posey and Briscoe are both Black.

According to the initial complaint filed by Posey, the assistant principal at the school admitted in a recorded phone conversation in August 2020 that she was aware of the class separation Briscoe created, noting "class lists are always tough" and that she wished the school had more Black children. The district's chief academic officer also acknowledged in a recorded conversation in March 2021 that Briscoe admitted to designating classes for Black students, the complaint states.

Posey told CNN's John Berman in September 2021 that she found out about the school's practice when she requested her child be placed in a certain teacher's class. Briscoe, she said, told her that was not a "Black class" and that her daughter would not have anyone who looks like her in the classroom.

After Posey filed her complaint, Ian Smith, who heads the Atlanta Public Schools' Office of Communications and Public Engagement, told CNN that the district conducted a review of the allegations and that "appropriate actions were taken to address the issue and the matter was closed."

Smith added: "Atlanta Public Schools does not condone the assigning of students to classrooms based on race."

On Tuesday, Posey told CNN she launched a second complaint on August 29, 2022, after she was fired from her role as an after-school care provider for the district, claiming her firing was "retaliation for raising the issue of segregation." Her husband, who was a school psychologist at Mary Lin, also left the school.

Responding to the claims, the district sent CNN a statement that read, "Atlanta Public Schools has received notice from OCR that a complaint was filed, and the district is following OCR's process. Given that this matter is pending before a federal administrative agency for consideration, APS has no further comment."

"To our knowledge, we do not believe they have gone back to that practice," Posey told CNN regarding her claim of segregated classrooms. "My understanding is that they had changed to some degree, but there were rooms that were not diverse."

The segregated classrooms claim shook up the predominately White and affluent community. It's also fueled a debate about whether the practice would even be considered legal or productive for the children.

In the spring, two members of the Atlanta branch of the NAACP visited Mary Lin Elementary to see whether there was merit to Posey's claims. Marilyn Barnett Waters, who at the time was the Georgia state education chair of the NAACP, told CNN she believed the school staged some of the classrooms for her visit.

"I saw African American students, in two of the classes I saw. It almost seemed like they were foreign to that class," Waters told CNN by phone Wednesday while recalling her visit. "The Black students weren't engaged with any of the other kids in the class."

"The White children seemed to have friends, but the two Black girls were sitting there, and it didn't seem like they knew each other. They kept watching me as if I was going to say something to them," she said.

Waters added there were a lot of classes that were not in session, but of those she did see, she "did not believe that the quality of education was really high."

"I saw a lot of students without direct instruction," she said.

In a statement to CNN, Atlanta Public Schools said Waters' assertion that the school setting was staged "is totally fictional."

The principal was accommodating during the visit and answered all of Waters' questions, the district said.

"When asked to give her impressions of what she observed during the visit, Dr. Waters stated that all she saw was 'a normal school day happening," according to the district.

"It is both troubling and disappointing that Dr. Waters has chosen to provide you with false statements that are an affront to the faculty and staff."

Mary Lin Elementary School is number 14 in the state and first in the district for all test scores, according to Atlanta Public Schools.

The school was founded in 1929 and there was a time in history when the school was all White. However, by the mid- to late 1990s, the racial demographics of the school were such that no classrooms were all White or all Black, according to APS.

The elementary school has 599 students in grades kindergarten through fifth grade, according to the Georgia Department of Education's latest data. Of those, 60 students are Black, according to the ethnicity/race breakdown.

Overall, public schools in Atlanta are predominately Black, according to recent data. As of October 2021, the racial demographics of Atlanta Public Schools students are 72% Black; 16% White; 8% Hispanic; 3% two or more races; 1% Asian; and 0% American Indian.