The complaint alleged Matthews' termination was part of a pattern of discriminatory practices the "predominately Caucasian" school has engaged in for years.
"Historically, black employees," the complaint says, "regardless of their position, have been denied promotions and are subject to harsher discipline, unfair demotion, and unjust termination in circumstances where nonblack staff are, or have been, treated more favorably."
A spokeswoman for Springside Chestnut Hill said Friday the school does not comment on pending litigation. The school has until Jan. 14 to file its response to the complaint in federal court.
Matthews had been teaching upper-level math at the school since 1998, was an assistant softball coach, served as the faculty representative for an organization that promotes cultural diversity, and was a senior project adviser.
The suit says the instructor had an unblemished record until August 2012, when Sands issued a written warning and suspended him from his coaching and other advising duties because she said he had violated school policy by exchanging texts with a young woman who graduated in June. The suit does not specify when the alleged texts were exchanged.
Matthews maintains that school policy does not prohibit teachers from texting students.
Court documents say Sands sent a letter to several parents that said the school had investigated the matter "and concluded that, although the text-communications were personal, they were not sexual in nature." She said that Matthews had used poor judgment but that there was no evidence to suggest he was a threat to students.
But, the lawsuit says, the school was abuzz with rumors that the source of the complaints about Matthews was the daughter of an administrator who claimed Matthews and the young woman "had engaged in an immoral personal relationship."
As gossip spread, the suit says, some parents "demanded Mr. Matthews' removal, threatened to send their kids elsewhere, or to remove them from his class. At least one student was withdrawn from Mr. Matthews' math class."
Saying new information had come to her attention, Sands called Matthews to a meeting Sept. 11 and demanded that he confess to improprieties and resign, the court filing says. When Matthews refused because he said he had done nothing wrong, Sands fired him, it says.
Rather than investigate the rumors, the suit says, Sands and the school relied on accounts of third parties to wrongly terminate Matthews, violated his privacy, and defamed him by disseminating "erroneous findings of his alleged wrongdoing" to the school community.
Springside, a former girls' school, and the adjacent Chestnut Hill Academy, a former boys' school, merged in 2011.
Annual tuition ranges from $17,250 for prekindergarten to $29,250 for high school.
Contact Martha Woodall at 215-854-2789 or firstname.lastname@example.org.