Parent Georgy Cohen spotted the poem taped to a classroom chalkboard at the school in the city of Somerville.
"This sort of thing really makes me question raising my kids in the USA", tweeted one San Francisco-based father.
She and Somerville Public Schools declined to identify the school, but district officials confirmed it was the work of one teacher and is not used across all of the city's schools.
The post garnered a wide response from parents whose children have had similar disguised safety lessons taught at school, including a stealth game which involved children hiding in the corner until it was "safe". Now it's time to have some fun!'
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.
She told the Boston Globe she found the image "jarring", adding: "When I was in kindergarten, we had fire drills".
"These are the things they unfortunately have to do", Cohen told the newspaper.
Ms Cohen came across the poem while touring the school her child will attend after the summer holidays. When ask what that was, she said "in case a bad man comes to our school we have to help Mrs.M push her desk in front of the door, get in the closet, hold hands & be VERY quiet!"
"To be shocked by it is important".
They agreed with Cohen's initial assessment of the circumstances, calling the need for lockdowns "jarring" for students, educators, and families. "Stay outraged. And if it gets somebody to do something - to give money to an organization or to call their representatives. then great, I think that that's important".
Much like fire drills in past generations, lockdown drills are now common practice in schools and won't be going away anytime soon, according to the statement.
Ms Skipper said she agreed that active shooter drills were "jarring" for both children and staff, and rued that the poster - while creative - "speaks to a loss of innocence".