(CNN) The Boston school superintendent, who announced he's resigning after a lawsuit accused Boston Public Schools of sharing information that led to a student's deportation, denied the allegation Monday, saying such an act would defy school system policy and his personal politics.

The lawsuit was filed Thursday by the Lawyers' Committee for Civil Rights and Economic Justice , the nonprofit group said in a news release, along with "a coalition of students' rights groups."

Superintendent Tommy Chang said in a Monday letter that Boston Public Schools had not received the lawsuit yet, but he was taking the unusual tack of speaking out because of "how strongly we, as an organization, and I personally, as an educator and an immigrant, feel about protecting immigrant children."

The groups are suing to obtain records to "understand the extent to which BPS shares such student information" with the Boston Regional Intelligence Center, known as BRIC, which the lawyer's group described as "a network of local, state, and federal law enforcement agencies, which includes (Immigration and Customs Enforcement)." The group said in a news release, "BPS refuses to share any information."

"The students' rights groups filed their initial public records request upon learning of an East Boston High School student who was deported based, in part, on the report of a run-of-the-mill school incident that was shared by Boston School Police with ICE via the BRIC," the lawyer's group news release states.

The "school incident" refers to two students who attempted to start a fight, but were unsuccessful.

Chang said in his Monday letter, "That claim is false. BPS would never give student information to ICE, unless required under law."

Boston Public Schools, he wrote, does not request or keep records on the immigration status of students, and even if authorities presented a warrant for student records, only the school's legal team could make the call on whether to comply.

During the incident in question, local and state police were investigating gang-related murders that occurred more than two years ago in East Boston, and BPS provided authorities with school police reports, he said.

"The information provided did not contain any reference to an individual immigration status," Chang wrote.

He did not explain the reason for his abrupt departure. Previously, neither Chang nor Mayor Martin Walsh gave a reason for his resignation.

And while Chang's resignation letter and the school district did not say when the resignation will become effective, CNN affiliate WCVB reported Chang will be leaving his post before the start of the new school year.

"Immigrants make this nation strong," he wrote in his Monday letter. "Like so many people, I'm horrified by some of the actions our federal government is taking, particularly against immigrant families, actions that I believe are fundamentally contradictory to what this country stands for. I have long spoken out on the need to protect immigrant students, and will continue to do so."

A native of Taiwan, Chang moved to the United States at 6 years old, the school district's website states. He said in his farewell letter Friday that public school teachers guided him on his educational journey, including learning English.

"In this moment more than ever, I want every immigrant child to know that's the country America strives to be, must be, and will be," Chang said.

Walsh said in a statement that he and Chang "mutually agreed that there needs to be a change in leadership."

"We need a long-term education leader with a proven record in management who can gain the confidence of the community on the strategic vision for the district and execute on the many initiatives that have been identified as priorities for our students and schools," the mayor's statement read.