NEW YORK - Alarmed at the US Justice Department's retreat from a full defense of transgender rights, four advocacy groups have urged the Trump administration to maintain Obama era guidance to public schools on protecting transgender students.Advocates for lesbian, gay, bisexual and transgender (LGBT) rights sent a letter dated Monday to Attorney General Jeff Sessions and Education Secretary Betsy DeVos, urging them to preserve guidance sent to public schools last year.That guidance urged schools to allow transgender students to use bathrooms matching their gender identity and issued other directives on bullying and harassment."Each of these guidance documents is based on years of careful research to accurately reflect a substantial body of case law and proven best practices from schools across the country," the letter said.President Donald Trump has spoken in favor of LGBT rights and in January the White House vowed to defend LGBT workplace protections issued under former President Barack Obama.But LGBT advocates say Sessions and DeVos are more conservative and question their commitment to transgender rights. Asked to comment, a Justice Department spokesman would only say the department received the letter and will review it.Texas filed a lawsuit seeking to block the Obama guidance and was joined by 12 other states. They said the federal government overreached in trying to force social policy on them and threatening to cut off federal funds to states that failed to comply.A US district judge sided with the states and blocked the directives. The Justice and Education departments under Obama appealed.On Friday, shortly after Sessions was sworn in, the Justice Department withdrew a motion in defense of the guidance, acceding to the lower court judge's injunction to block it nationwide."It's really upsetting to see that the first thing they chose to do, late on a Friday night, was take a step back from fighting to defend students from harm," said one of the signatories, Eliza Byard, executive director of GLSEN, a group advocating for LGBT students.The letter was also signed by the leaders of the National Center for Transgender Equality, Human Rights Campaign and the National Women's Law Center.Major issues of how schools must deal with transgender students could be settled in a case due to be argued before the US Supreme Court in March.The case pits a Virginia school district against a transgender boy fighting for his right to use the boys' room at his high school.