What's the celebration they had on the roof

The group celebrated the completion of the roof and signing of the constitution.

From the text:

On the night of January 16, the ghostly old school building came mysteriously to life. Lights filled the upstairs windows, and there was joyous shouting and ex- citement on the roof. The glow, of a dozen torches dot- ted the roof line. Horns blared, and a hundred dogs barked as if to drown out the sounds above them. To the silent audience below, Glenbard looked like a castle.