New York state’s education officials are calling on schools to make sure students feel safe in the wake of a wave of post-election bullying and harassment.

In an unusual joint letter to school leaders, Education Commissioner MaryEllen Elia and Attorney General Eric Schneiderman urged school districts to review their policies to prevent bullying, harassment, and discrimination — and improve them if necessary. The letter was sent in response to “a number of disturbing incidents” of hate-based acts and violence across New York in the past week, it says.

“Students must feel safe in the classroom to be able to learn,” Elia said in a statement. “It is our responsibility to foster an open dialogue with students and employees about discrimination, harassment and intimidation and send a strong message that these types of behaviors will not be tolerated in our schools.”

The letter comes after Governor Andrew Cuomo asked Elia to require anti-discrimination trainings for staff and students on Tuesday. The commissioner’s letter says she will “strongly encourage” schools to hold anti-bullying meetings.

Nationwide, the Southern Poverty Law Center has logged more than 400 incidents of harassment and intimidation since the election of Donald Trump, who used racist and anti-immigrant rhetoric throughout his campaign.

In New York City, many students have expressed fear that the election results could erode tolerance for immigrants, Muslim students, and LGBTQ youth. Some have even walked out of class to protest the election results.

Sending a letter to schools puts New York’s education officials in line with policymakers across the country. In Los Angeles, school board members voted to affirm their current policy that Immigration and Customs Enforcement agents cannot enter school grounds unless previously approved. Denver’s school board passed a resolution committing to quickly addressing incidents of discrimination or harassment.

In New York City, education department officials said they will rely on their existing rules to keep schools safe.

“We have explicit protocols and robust training programs in place requiring all incidents to be reported, investigated and appropriately addressed,” spokeswoman Toya Holness said.