To the melody of Twinkle, Twinkle Little Star, the lyrics are rewritten telling students what to do if there is an active shooter in the school.
Cohen said he isn't upset with the classroom teacher for hanging up the poem.
"This should not be hanging in my soon-to-be kindergartner's classroom", the tweet read. "A part of me is glad they showed her, and another part of me is just sick that it had to happen".
The post has already been liked and shared more than 60,000 times with many other parents sharing their outrage that the spate of school shootings had inevitably led to this.
Cohen later clarified that she feels the school's measures are appropriate and that her post was meant as a cultural comment on the necessity of such a measure. "It's all done / Now it's time to have some fun".
Cohen saw the photo while she and Healey were touring the school, where their daughter will attend kindergarten next fall.
"These are the things they unfortunately have to do", Cohen told the newspaper.
Social media reacted with surprise, shock and worry about the poem, according to Mashable.
And, as one user added on Twitter, some adults might also remember nuclear bomb drills that were a part of some schools in the 1980s.
The 2012 massacre at Sandy Hook Elementary School, in which 20 children between the ages of six and seven were killed, is the fourth deadliest mass shooting in the United States to date.
In a statement, Superintendent Mary Skipper and city Mayor Joseph Curtatone applauded the teacher's creativity, but they lamented that lockdown drills have become as common as fire drills. And in place of the usual self-promotion following a tweet going viral, the mom simply requested that people call their congressional representatives to advocate for gun reform or support organizations like Everytown and Sandy Hook Promise.
"Students in Somerville and across the country know how unnatural this is, as evidenced by their vocal leadership and advocacy this year in response to continuing school shootings", the statement said.