SOMERVILLE (CBS) – A “jarring” nursery rhyme posted in a Somerville classroom to help prepare young children for a lockdown is going viral.

Georgy Cohen tweeted a photo of the rhyme on Wednesday, saying “this should not be hanging in my soon-to-be-kindergartner’s classroom” at Arthur D. Healey Elementary School.

This should not be hanging in my soon-to-be-kindergartener’s classroom. pic.twitter.com/mWiJVdddpH — Georgy Cohen (@radiofreegeorgy) June 6, 2018

There were strong reactions on social media to the poem that has lines like “Shut the lights off, say no more” and “Go behind the desk and hide, wait until it’s safe inside.”

“And now it’s time to have some fun” This Literally makes me sick to stomach. — 🗻 (@hazelandbay) June 7, 2018

Chilling. What does the NRA have to say about that??! More importantly, what do our representatives think about it?? — MoCole (@MoCole1) June 7, 2018

It broke my heart when I had to explain the reason for lockdown drills to our then-kindergartener – during their first drill, a child in her class was whispering about a man with a gun and how they were all going to die. We live 40 minutes from Sandy Hook. — Katie Sherrick (@katiesherrick) June 7, 2018

Mother Sana Bazzaz told WBZ-TV that the poster is a useful way to help protect children. “It’s not scary. Just in case they really need to do it, the kids can rhyme to the song and do what’s needed to be done.”

Somerville Mayor Joseph Curtatone and Superintendent of Schools Mary Skipper released a joint statement on Thursday, reflecting on the heightened attention to school safety in the wake of a series of deadly school shootings.

“As much as we would prefer that school lockdowns not be a part of the educational experience, unfortunately, this is the world we live in. It is jarring – it’s jarring for students, for educators, and for families,” the statement read. “This poem is an example of how one of our educators used a rhyme to help her young students stay calm and remember the key steps they would need to follow during a drill or real emergency.”

Somerville city officials also included a statement from Jack Torres, 16, who is the sophomore class vice president and CEO of anti-gun violence group “50 Miles More Mass.”

“Lockdown drills are necessary in this country because until stronger gun reform laws are enacted and the plague of gun violence eradicated, there must be systems in place to keep our schools and students safe,” he said.

Cohen’s tweet had more than 22,000 retweets as of Thursday night.