POTOMAC, Md. (AP) — The private school that Barron Trump attends has joined other schools in calling for gun control.

St. Andrew’s Episcopal School and more than 100 schools in Maryland and the Washington area on Wednesday signed an open letter calling on Barron Trump’s father, Republican President Donald Trump, and Congress to support gun control measures and to reject arming teachers. The White House has proposed arming educators.

The schools support a “robust system of registration and background checks” with an emphasis on assault weapons. They also back stronger mental health services.

The letter was published as tens of thousands of students walked out of their classrooms Wednesday to demand action on gun violence and school safety. The walkout was triggered by the Feb. 14 massacre at Marjory Stoneman Douglas High School in Parkland, Florida.