Referred to as “B.D.” in court filings to protect her identity, a teenage Muslim girl converted to Christianity allegedly due to her teacher’s active proselytization during public school hours.

That is the center of a long-running legal back-and-forth over religion at Jacobs High School in the northwest Chicago suburb of Algonquin, Illinois.

The teacher, Pierre Thorsen, taught world history and world religions and also sponsored a student Christian club called Uprising.

B.D.’s parents, Chaudhry and Alvi, sued Thorsen and the school district, alleging that the district should have been aware that the teacher—who in 2015 was named the county’s Educator of the Year—had been actively engaged in using his position at the school to proselytize students.

According to the complaint, “Thorsen would repeatedly engage in conversations with students before, during, and after school where he would advocate for his faith and cast doubt, belittle, or discount other faiths.”

In an amended complaint, the parents further alleged that after her conversion, Thorsen introduced her to church members who offered to take her in if her family disowned her.

Thorsen denied the allegations and defended his discussions of religion in public school. He said there was no attempt to convert B.D., but rather a suggestion that she direct her faith questions to other Muslims.

After Chaudhry and Alvi gave their story to a local paper, Thorsen counter-sued the couple for defamation.

Meanwhile, Judge Iain D. Johnston of the U.S. District Court for the Northern District of Illinois, Eastern Division, dismissed the couple’s complaint against the school district, ruling that “The fact remains that when the Parents informed the District of their concerns about Thorsen, he was investigated, disciplined, and transferred to another school — a sequence that hardly raises the reasonable inference that the District had previously known of and ratified Thorsen’s conduct.”

The parents will appeal but will need to wait until after their still-pending case against Thorsen is decided.

The school district, however, is on the receiving end of another lawsuit, this one filed by Thorsen who contends that the officials discriminated against his Christian faith, restricted his ability to talk about religion with his students and pressured him to quit because talking about Christianity made people uncomfortable.

In his complaint Thorsen alleges, “Defendant [the school district] otherwise created a hostile environment, intolerable conditions, and undue restrictions against Christianity.”

Religious freedom, definition of; freedom of speech, restriction of; and religious tolerance, boundaries of have become thorny, often emotional points of conflict, suits and counter-suits—with America’s public schools as the battleground.

Last year an assistant football coach, fired for conducting postgame prayers on the field, won his job back after the U.S. Supreme Court found in his favor under the U.S. Constitution.

Also last year, a West Virginia school board mandated once-yearly religious freedom training as part of a settlement of a complaint lodged by four families contending that their children—including a Jewish child—were compelled against their will to attend an evangelical revival meeting at an assembly in the school.

While student-led religious groups are allowed at schools, and outside groups can run religious activities on weekends or after school, teachers and other school officials are barred from promoting their faith to students. But it’s a tricky, often blurry line to navigate, especially in a school environment where curious and impressionable teens are mixed in with adults with certainty of their faith and who want to tell the world about it. The jury is still out.