Hot-tempered actor Sean Penn was scheduled to be released from Los Angeles County Jail early today after serving about half of his 60-day sentence for assaulting a movie set extra and reckless driving, sheriff's deputies said. The 27-year-old star of such films as "Fast Times at Ridgemont High" and "Bad Boys," was sentenced to 60 days behind bars in June for violating his probation on a battery conviction, but the term was shortened because of good behavior. Penn violated probation by hitting a movie extra on the set of his yet-to-be released movie "Colors" and for reckless driving. Penn, the husband of pop superstar Madonna, first served six days in the Mono County Jail in Bridgeport, then was released so he could perform in a movie. He re-entered the 6,500-inmate Los Angeles County Central Jail Aug. 22 to serve the remainder of his sentence.