The measure poses an excruciating dilemma for Texas schools that have quietly agreed at parents' requests to keep secret the birth genders of some students. To comply with state law, teachers might have to send transgender students to the bathroom of their birth gender or to a single-occupancy bathroom, shocking their peers. The legislation "really boxes in school systems," said Raffi Freedman-Gurspan, a spokeswoman for the national transgender rights organization Trans Equality. Supporters revived it late Sunday, advancing a proposal applying only to the state's public schools, which educate about 5.3 million students. Currently, each school and school district determines how to handle students whose birth genders are secret — a small portion of Texas' thousands of transgender minors. [...] Lindsey Pollock, a principal in another school in the district, said she tries to stick up for children, even under legal and political pressure. Just last year, a transgender girl entered kindergarten in Pollock's Garden Montessori elementary, asking to keep her background secret. [...] teachers at most Texas schools that are hiding students' birth genders are too afraid to take a public stance and are bracing for a crackdown by the state. Lauryn Harris, an advocate for transgender children in San Antonio's public schools, said teachers have expressed "great empathy and concern" for students but have also been warned to change their practices. Most of the time, it's not going to be noticeable, but kids mess around a lot especially in places like bathrooms, where they're together and there's not always adult supervision. Texas Rep.