Calling hasmat.
Just about every high school currently has hundreds of fluorescent tubes in use and have had them for about 50 years. Most of them last 10 years each and recent ones have the same mercury content as CFLs.
Even the EPA does not suggest calling hazmat for breakage.
http://epa.gov/cfl/cflcleanup.html
They say to leave the room, open windows to air it out, turn off air circulation systems to the room, cleanup the pieces, and dispose of them in a sealed container.
At worst the kid should get in trouble for broken glass on the floor.