The Hole (2001)

Genre: Horror / Crime / Drama / Mystery / Thriller
Starring: Thora Birch, Desmond Harrington, Daniel Brocklebank, and Laurence Fox
Country: UK
Language: English
Tagline: Desperate To Get In. Dying To Get Out.

Plot: Four teenagers at a British private school secretly uncover and explore the depths of a sealed underground hole created decades ago as a possible bomb shelter.

http://www.imdb.com/title/tt0242527/
http://en.wikipedia.org/wiki/The_Hole_(2001_film)