Firstly, if you're not already a fan of Gintama this is not for you.

Now, assuming you are a fan, this show will give you more Gintama. In many ways this show feels like an extended Gintama bit, like if the Mantama bit went on for 12 episodes instead of 1. You get to see more of the characters you know and love (Although...) and get more of Gintama's comedy and occasional emotional moment or lesson.

THE CHARACTERS

A lot of characters also feel a bit more one note, like they've been reduced to just their running joke(s). Some characters get more to work with then others, and some are definitely left directionless without the context and position their character in the anime.

Some transition well into their roles in a school. Prince Baka and his butler probably fair the best and fit seamlessly into their roles. The shinsengumi into disciplinary committee works well enough. Gintoki as the teacher Ginpachi worked, although it took a bit to get used to the idea of him being older than the rest of the main cast (and the students being all roughly the same age for that matter. Kagura and Kondo do not look like it). The shimura's both fit in well enough as they were both kinda the "normal" people of the cast already. Kamui works well as a delinquent, they barely have to change him at all.

Everyone else kinda loses something. Katsura and elizabeth feel like they're missing something to replace them being Jouishishi. It feels like the show doesn't know what to do with Kagura, she's only prominent in a couple episodes and while she does have a familial connection to Kamui (who is important) it only even gets brought up once.

Takasugi feels very directionless, although the anime itself does call this out in episode 11, as usual Gintama has always been self-aware. It's kinda hard to criticize this show when it's clear that it often directly acknowledges those criticisms. That said, being self aware doesn't automatically shield from any criticism.

I also feel like some characters (ok, it's toujou. I'm not the biggest fan of toujou. I really don't like him. Why did he get so much screen time? Why Why Why? Was his VA really Cheap or something?) got too much screen time, while I feel like some should have had more screen time like kyuubei (the annoying stalker get more screentime), kagura. Of course, with only 12 episodes compared to Gintama's 369 it's expected that there wasn't enough time for all characters to get the spotlight.

THE PLOT

It's a mostly episodic affair this time, with the only real multi episode affair being takasugi and gang and their story. It all culminates in what feels like it should be a final episode with episode 11. The takasugi plot line was pretty good, and actually addressed some issues I was feeling with the show through it's very meta conclusion. It feels very much like an early Gintama arc in that it's only in a few episodes and surrounded by episodic comedy.

I feel though, that it wasn't quite enough. Personally, one of the best things about gintama is how it combined episodic comedy with these overarching plot threads that would culminate in genuinely quite good "serious" arcs (although, even the serious arcs still have their comedy). It was that combination of irreverent comedy and well written "serious" story arcs that truly made Gintama for me. While the takasugi arc was something here, it didn't quite scratch that itch for me.

The one-off emotional/moral lesson episodes were nowhere near the level they are in gintama. At best, they reached the level of a mediocre episode from the main show.

The conclusion to the takasugi arc was probably the best part of the show. It directly calls out the nature of the show as an unnecessary add-on to a finished franchise. A cash-grab made without any real reason beyond making more gintama to prolong the franchise.

SETTING

One of my favourite things about Gintama (other than the characters) is the wonderfully weird world. A fusion between bakumatsu era and modern japan with aliens scifi and occasional fantasy/supernatural elements. It was the perfect backdrop for Gintama.

In contrast, I think Gintama High is a decent setting - just not as interesting. Considering there were only 12 episodes to explore it though, I'm not too bothered.

MISC

Ginpachi-sensei as a show feels a bit fake at times. At several points different characters (I think mostly just takasugi and gintoki/ginpachi) refer to "playing along", and that is what it feels like the whole cast is doing. It feels less like a school anime and more like the cast of Gintama playing at being in a school anime. I think this is largely intended, although it makes it harder to actually get invested in the characters and the world when the characters themselves don't seem to believe it either.

It kinda feels like the anime itself isn't trying very hard, like its almost here by contractual obligation or something.

Again, it feels a bit like if the mantama bit was stretched to 12 episodes. It was almost like I was subconsciously waiting for the whole school bit to end and them to go back to usual Gintama programming.

A lot of this is addressed by the episode 11 conclusion, but addressing it doesn't make it go away.

CONCLUSION
It was nice to see the cast of Gintama back again, and I am definitely heavily biased in favour of this show (I am someone who is very susceptible to "here is more thing of thing you like"). A recommend for fans of Gintama, although don't go in expecting peak Gintama - more like a kinda average set of episodes somewhere in the middle where the cast act out being in a high-school anime for 12 episodes.

The season ended with the teaser of there potentially maybe being a season 2 happening sometime maybe. If that season 2 comes out, I would watch it. I think most fans of Gintama agree that the early episodes of Gintama aren't Gintama at its best (I definitely enjoyed them, but they weren't peak gintama), hopefully if this does get a second season it can develop more of its own identity.