Whats that one movie where kids in a school find a cave inside the school?

I remember watching a move when i was around 7 years old (about 7 years ago) and there were these kids in a school and there was a vent in the school they said was haunted then they dared a kid to go in the cave and there is somekind of monstor in there and there are skeletons in there when the people go to check it out it was dark and they had to use flash lights. great help would be much appreciated.