PITTSBURGH (AP) — Chalk it up to a good-natured joke, but a Pittsburgh school teacher might have a new record on his hands. Or at least sitting on the floor of his classroom.

Three students made Bishop Canevin High School history teacher Joseph Romano a 270-pound piece of chalk as a joke after noticing his affinity for oversized chalk.

Matt Durbin, Nick Sylvester and Terry Dougherty mixed plaster and water in a trash can to make chalk similar to the kind used on sidewalks.

The result is effective, even if a bit unwieldy. Romano has taken to chipping off chunks as he needs them.

Sylvester has filled out an application for a new category to Guinness World Records. But even if they don’t get a record out of it, Romano has given them extra credit.