I was never a huge fan of this show. However it had a few good episodes in the first few seasons. IMHO the show jumped the shark when they started to put on plays. OMG a 2 part for a play on Little Shop of Horrors? Wow were the writers L A Z Y. Then more plays in the upcoming seasons.
I would also say when Richard Pryor's daughter showed up but it was not her fault the show had limited writing about a class of smart kids. IMHO it was a rip off of Welcome Back Kotter instead of Sweat Hogs, it was a brilliant bunch. However just like WBK, it was only good for 2 seasons

The plays/musicals were definitely JTS material. It was SO obvious everything was fake and they lip-synched to voices that weren't theirs and it was painfully obvious. The last season was just borderline terrible but the first few seasons were definitely good and quality seasons and were enjoyable. But the plays/musicals were cringeworthy and fake.

So I never saw the show in its original run so streaming it now on HBO Max feels like a brand new show to me but I'm just about done with the series and so far I've noticed a few things that would be JTS moments.

For one the show has too many characters trying to fight for screen time that not all get their chance to have a spotlight episode, Dennis and Arvid seem to have more scenes because their the most fun while Alan is the dullest from the group.

When Billy Connoly joined the show as Howard Hesseman's replacement he seems to bring his stand-up routines with him as each episode now usually involves Billy telling a joke in the cold opening.

The fourth season, I'd say. I didn't much care for the new students.

On a side note, two episodes filmed during the third season ended up airing during the fourth, though on HBO Max, they're just tacked on as the last two episodes of season 3. (That happened, too, with an episode of two from the first three seasons on Max, showing up in the season in which it didn't actually air, but was produced.)

They added the annoying new-age Viki character.

The loss of Howard Hesseman is where it JTS. Billy was terrible.

That's when it not only jumped the shark, but caught it, broiled it and served it for dinner. :D

True, Mr. Moore made season 4 somewhat tolerable, though it was not as enjoyable as the previous three seasons.

That's when it not only jumped the shark, but caught it, fried it and served it for dinner. :D

True, Mr. Moore made season 4 somewhat tolerable, though it was not as enjoyable as the previous three seasons.

Yeah, I can understand the perspective of JTS after season 3, too, though, because the new characters were not as good as the originals.

The loss of Howard Hesseman is where it JTS. Billy was terrible.

I agree. I liked the show a lot until Howard left the show...once he left I didn't really like the show's vibe with the new teacher and the remaining/new students.