Black will stay sober on movie sets

Jack Black has vowed to stay sober on movie sets - because he would never be able to work competently while under the influence.

The actor admitted that many film stars find it easy to disguise the fact that they have been partying wildly before arriving on set.

However, following a frightening experience in high school, Black has realised that he would not be capable of fooling his bosses.

"I had an improv class in high school and I came stoned one time. I was so paranoid that I never tried to f*** with it again," Black explained. "I marvel at some people's ability to party and then act. I'm not built that way."

Black recently confirmed that he has signed up for a second School of Rock movie.