Unfortunately the full study itself is behind a paywall, but summaries are available from many news sources online.
Original Study Publisher: Pediatrics. May 2019. Authors: Gabriel R. Murchison, Madina Agénor, Sari L. Reisner, Ryan J. Watson.
“Transgender adolescents may be less likely to be sexually assaulted when they can use school bathrooms and locker rooms that match their gender identity rather than their sex assigned at birth, a U.S. survey suggests.”
“The survey of 3,673 trans and nonbinary teens in American middle schools and high schools found that more than one in four reported being sexually assaulted in the previous 12 months.'“
“When schools required students to use bathrooms and locker rooms based on their sex assigned at birth, transgender boys - who identify as male but are labeled female on their birth certificates - were 26 percent more likely to experience sexual assault.”
“And transgender girls - who identify as female but were assigned male at birth - had more than twice the assault risk when they had to use restrooms and locker rooms for boys.”
“… the results add to the evidence suggesting that failure to support trans and nonbinary youth can endanger both their physical and mental health, Rosenthal and Ehrensaft write.”
“' ‘Transgender youth who express their gender identity but are required to use facilities matching their genitalia are not only at risk for verbal and physical harassment, including sexual abuse, but, not surprisingly, some will avoid using restrooms altogether, resulting in increased risk for inadequate fluid intake, urinary retention, urinary tract infections, impacted bowels, and school avoidance,’ they write.”