After only two rapes and a handful of murders, you're so grateful that you can almost look when a bully takes a little something from his nose and mashes it into Sean Penn's beans. Penn plays with "Bad Boys," kid crooks in a Chicago pen.

It isn't exactly jailhouse rot, but it doesn't exactly have a clean rap sheet, either. Director Richard Rosenthal knows how to make you nervous, for sure, even when the blood looks like ketchup and the bruises like kohl. Rosenthal's latest -- not his first offense -- follows "Halloween II," a classic of the slasher school. No more fooling around. Now, he's ready to pay his debt to society.

Then producer Robert Solo goes and gets noble, too. He asked scriptwriter Robert Di Lello for "a young Jimmy Cagney, caught up in today's juvenile world of street crime and punishment." But Di Lello is no Dostoevski and Penn is no Cagney. The story is as stale as prison air and so is the star.

Penn, who scored as a doper surfer in "Fast Times at Ridgemont High," just isn't cocky enough for this tough stuff. No swagger, no lip, no leadership. He plays an incorrigible hood who's sent to a juvenile jail outside Chicago on a manslaughter charge. He's glum and gnarly.

Costar Esai Morales has more muscles and a prettier mugshot. But Morales turns vicious when Penn plows over his kid brother in a dope misdeal. He goes and rapes Penn's screen girlfriend (Ally Sheedy) to get sent up so he can take Penn out.

The central rivals, supported by extras from a real juvenile facility, are also backed by an ecumenical and racially balanced cast of criminals -- including a Jewish psychopathic bomber and a blond called the Viking. There are also kindly, but inept, guards. One, the house psychiatrist (Reni Santoni), urges Penn to come back to the family of man.

Santoni also reminds Penn that time stands still on the cellblock. We already know, it's pokey in the pokey -- the sentence is 123 minutes long. BAD BOYS -- At area theaters.