By Veronica Stracqualursi, CNN

(CNN) -- The school attended by President Donald Trump's youngest son joined an open letter demanding the President pass gun legislation to protect students.

Robert Kosasky, the head of the St. Andrew's Episcopal School in Potomac, Maryland, is just one of more than 100 independent school heads in the area calling on Trump, Congress and state leaders to "enact specific, rigorous measures to reduce gun violence in our society, particularly in our schools."

The open letter, which was first published in The Baltimore Sun and obtained by CNN, pushes for a "robust system" of background checks and stronger mental health services.

The school heads also disagree with one policy Trump has been in favor of -- providing some school personnel with "rigorous" firearms training to carry guns in classrooms.

"What we do not need is to arm our teachers with guns, which is dangerous and antithetical to our profession as educators," the letter said.

Trump and first lady Melania Trump's son Barron, 11, began attending the school in Potomac, Maryland last year.

The letter was published on the same day of a national school walkout in which thousands of students demonstrated and rallied for new gun laws, including outside the White House.

The Trump administration on Sunday night proposed providing some school personnel with "rigorous" firearms training and backed a bill to improve criminal background checks on gun buyers, but backpedaled on the idea of increasing the minimum age to buy certain firearms -- a policy Trump had said he would support.

The proposals, which come more than three weeks after the Parkland, Florida, school shooting, also include a plan to establish a commission chaired by Education Secretary Betsy DeVos that will recommend policy and funding proposals for school violence prevention, including possible age restrictions on some firearms purchases. The commission does not have a set timeline of when it will report its findings, although an official said it would be within one year.