I get why schools are jumpy. It’s not even six months since Newtown.

I don’t get why schools rush to make pint-sized offenders out of kindergartners who goof up by bringing toy guns to school or onto school buses — especially when those “guns” are hardly bigger than a quarter.

Yet, at least three times in four months, a toy-gun-toting Massachusetts kindergartner has run afoul of school authorities. It happened again on the bus to Palmer’s Old Mill Pond Elementary School last week.

I’ll give Palmer this much: The toy that caused the uproar on the school bus Friday looks like a tiny assault rifle. It’s from a G.I. Joe action figure. It’s less than 2 inches long, and the boy is 6.

“I think they overreacted totally. I totally do,” the boy’s mom, Mieke Crane, told WGGB-TV. Her boy had to write a letter of apology to the bus driver, though after she met with school officials yesterday, they agreed to drop the detention he had been sentenced to serve. Mom didn’t want to talk about it anymore. She handed off to an expert — her own mom, the boy’s grandmother. Sara Godek is a retired school principal from Connecticut, and had this to say:

“I would’ve said, ‘Put it away’ or ‘take it home’ or ‘I’ll hold onto it until the end of the day. You’re not allowed to bring toy guns to school or on the school bus. I know. But the poor little guy is already so upset about this. I really think they overreacted. The problem is, we don’t use our heads.”

Or maybe — fearing lawsuits or overwrought parents or missing a legitimate threat — jittery schools just enforce zero tolerance every single time.

Two months ago in Hopkinton, it was Jonah Stone, 5, facing a half-day suspension after he brought a toy gun to school. The boy’s mother appealed. The punishment was revoked. Before that, a Hyannis child, also 5, faced suspension from his school’s after-care program when he made a gun from Legos and pointed it at another child. The school claimed the discipline had to do with disruptive behavior. The mother disagreed.

Two years ago, also at Palmer’s Old Mill Pond School, a 9-year-old was summoned to juvenile court after bringing an Airsoft gun to school. But that, at least, had more legitimacy: an Airsoft looks real and fires plastic pellets.

I don’t like guns. I wouldn’t want toy guns in my child’s kindergarten or on the playground. But I also know that little boys have a truck, train and gun gene. They make guns out of anything: Thumb and index finger, a roll of paper towels. Sometimes they do sneak contraband toy guns into backpacks. They need to know that’s wrong.

For most eager-to-please 5- and 6-year-olds, that’s enough. They are, after all, in kindergarten.