"Teachers" is sort of hard to explain. It's a comedy that's full of attractive, relatively appealing actors, it's handsomely produced and it's a pretty good idea — a workplace comedy featuring a bunch of teachers at a public high school.

What's hard to explain is how "Teachers" could fall so flat. Calling tonight's premiere (8:30 p.m., NBC/Ch. 5) a sitcom would be giving it too much credit — there's definitely a situation, but there's precious little in the way of comedy.

Justin Bartha stars as Jeff, an English teacher at Filmore High School in New Jersey. He's a smart-aleck who spends an inordinate amount of time hitting on his female colleagues and pretending he doesn't much care about his job. But he does, of course, and he's a great teacher.

If only he told great jokes.

"If you flunk this paper, you flunk the class," Jeff tells a student. "And let me tell you why that's a bad thing."

"Because I'll be cheating myself out of an education," the student replies.

"Oh, yeah. That for sure," Jeff says. "But it also creates a mountain of paperwork for me and really eats into my not-doing-paperwork time."

This is treated as hilarious by the laugh track accompanying the lines. Although "Teachers" was shot in front of a studio audience, almost all the laughs sound like the canned variety.

No surprise there.

Rounding out the cast is Sarah Alexander as dedicated teacher Alice, who's the primary focus of Jeff's amorous attention; Deon Richmond as Phil's best friend, Calvin; Sarah Shahi as Tina, the hot new teacher who's the secondary focus of Jeff's amorous attention; radio host Phil Hendrie as Dick, the burned out, longtime teacher; Matt Winston at Mitch, the nerd; and Kali Rocha as principal Emma Wiggins.

They all do the best they can (which, in the case of Hendrie, isn't much), but the material is so weak they can't make it better.

Other than the lack of anything resembling actual comedy, the biggest problem is that none of the characters ring true. Good TV shows make you believe the characters are real people — watching "Teachers" is watching a bunch of actors trying desperately to pull this off.

They can't.

HERE'S A SURPRISE (OK, not really) for anyone who's ever heard Phil Hendrie's radio talk show — the man absolutely could not shut up during the January press tour session presenting "Teachers" to TV critics.

Which is not to say that he should have remained absolutely silent. It's nice when the people being asked questions provide answers — otherwise it's not much of an interview.