SOMERVILLE, Mass. (AP) — A Massachusetts kindergarten class is drawing attention for using a lullaby to teach students about lockdown drills. Taped to the classroom’s chalkboard is a rhyme set to “Twinkle, Twinkle, Little Star,” rewritten telling students what to do if there’s a shooter. It begins “Lockdown, lockdown, lock the door. Shut the lights off, say no more.” A mother visiting the Somerville school posted an image of the poster Wednesday to Twitter. It has been shared thousands of times.

This should not be hanging in my soon-to-be-kindergartener’s classroom. pic.twitter.com/mWiJVdddpH

— Georgy Cohen (@radiofreegeorgy) June 6, 2018

Georgy Cohen, who took the photo, tells The Boston Globe it was “jarring.” Online commenters say it’s sad children have to be ready for a shooting. Cohen and Somerville Public Schools declined to identify the school. The superintendent says lockdown drills are a sad necessity, adding that “unfortunately this is the world we live in.”