‘Class’ will be in session at 8

In the dark art of TV network scheduling, it’s generally accepted that when prime time starts at 8 p.m., you offer viewers an established show, so they don’t encounter something unfamiliar right away and, racked by terror and uncertainty, click the remote to another channel and hunker down for the rest of the evening under the sofa cushions.

But CBS is going to toss that precept out the window this fall, when its heavily promoted new comedy “The Class” will lead off Monday’s all-important comedy block.

The network announced Tuesday that “The Class,” previously set for 8:30 p.m., will move to 8 p.m. and help bolster “How I Met Your Mother,” a critically praised but ratings-challenged comedy entering its second year.

CBS is posting a high-stakes bet. “The Class” is the network’s sole new comedy this fall, and executives are praying the costly new series can boost a lineup that’s sagged in the ratings since “Everybody Loves Raymond” went off the air last year.

“ ‘The Class’ is a new show, so it’s going to get a lot of promotion,” CBS spokesman Chris Ender said. He added that viewers were already familiar with “Mother” in the 8:30 p.m. slot, so it made sense to keep it there.

“The Class,” from writer-producer David Crane, the co-creator of NBC’s “Friends,” is an ensemble comedy about a group of third-grade classmates reunited as adults 20 years later.

It’s an intriguing concept, but the pilot, directed by sitcom legend James Burrows, lacks inspiration and comes across as a hit-or-miss collection of gags and hammy character types rather than a fully realized show.

One clear benefit for CBS, though: Because rivals are airing dramas (Fox’s “Prison Break”) or reality (NBC’s “Deal or No Deal”), the network will have a monopoly on comedy during that hour.

Chappelle’s snippets score

How much do Dave Chappelle fans miss the wayward star? Quite a bit, to judge by the ratings for Sunday’s premiere of “Chappelle’s Show: The Lost Episodes.”

An average of 2.6 million total viewers tuned in to “Lost Episodes,” according to figures from Nielsen Media Research. Although that’s not a record -- “Chappelle’s Show” was the network’s top-rated show after “South Park” -- it was high considering that the show amounts to fragments of episodes from an aborted third season.

In what has become the stuff of TV legend, the volatile comic mysteriously left “Chappelle’s Show” last year in the middle of production and evidently has no plans to return.