A Texas community college fired one of its biology professors for teaching his students that sex was determined by X and Y chromosomes, according to a new report.

First Liberty Institute, a law firm that defends religious liberty for Americans, sent a letter to St. Philip’s College in San Antonio on behalf of the professor, Dr. Johnson Varkey, demanding the institution reinstate him after he was fired in January 2023.

“When teaching the human reproductive system, Dr. Varkey also stated that human sex is determined by chromosomes X and Y, and that reproduction must occur between a male and a female to continue the human species,” First Liberty stated in its letter. “In the course of teaching Human Anatomy and Physiology, he made these statements in every class for 20 years, without any incident or complaint.”