does it help if I say that 各担任 means “each homeroom teacher”?
あーこの紙か
ah this form
こういうのって普通に各担任がやればいいんじゃないですか
isn’t it better for each homeroom teacher to (hand these out) as usual?
それが職員室も一枚岩じゃないからなー
that is because…the staff room isn’t a united group
認める認めないでモメてるし
we’re disagreeing on whether we should or not…
I think he’s blaming them (and the other students involved) for causing all this hassle
Ohh that makes much more sense! I thought the change of topic was too weird 
I agree with this. I interpreted 一枚岩 (large slab of rock) as being a metaphor. The staff room is not one large slab of rock, it’s composed of lots of teachers with different thoughts and opinions.
the girl with the “sunburn”. This was a fun chapter! Shimeji and Majime are not the only two weird ones. Everyone is weird (by our standards), so the MCs are actually quite normal in their weirdness.
Regarding 一枚岩, it’s the same metaphor we use in English: “[any culture, subculture, or group] is not a monolith. It is made up of different people who think and feel different things.” That’s really neat.
It feels so good to get back to this! I was missing this sort of humor in my life. It was interesting to learn that Shimejime might not be as uniquely weird in this world as we thought.
April 3rd
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I am a bit late to the party, sorry about that!
What is (?) meant to convey? Is it a ‘fill in the blanks’ sort of thing? If so, what are we supposed to mentally fill in there?
OK, I have not read that far, but grammatically speaking, it would be が I guess? So maybe the teacher is telling them to speak properly in terms of grammar? (I’m sure this will be totally off 
)
Is it a joke, emphasising her lack of コミュ力 by putting in a ? rather than the correct particle?
My interpretation that the “?” is marking this as 先生 making up a new word on the spot. I believe this is not the particle か, but rather the kanji 力 (りょく) ( “communication power/ability” by shortening the コミュニケーション that she used in the previous panel and adding the generic suffix 力 )
yeah that’s how I read it as well. X力(が)高い is a pretty common pattern.
as an aside, you can tell it’s the kanji and not the katakana because it looks a little awkwardly big next to the katakana
kanji → 力 カ ← katakana
and mixed in the same word:カタ力ナ
it’s subtle and I only just noticed it, but it’s there 
This word has an entry in the dictionary. It is an abbreviation, so maybe that is seen as unprofessional/casual, especially combined with the missing particle?
I did a bunch of Googling to see how common each phrase was:
| Google search | コミュ力 | コミュニケーション能力 |
|---|---|---|
| X | 2,930,000 | 9,890,000 |
| Xが高い | 1,010,000 | 4,980,000 |
| Xの高い | 375,000 | 3,490,000 |
| X高い | 286,000 | 54,200 |
Each phrase with “が” or “の” is more common than the phrase without it, so I agree with @Micki. I’m guessing the (?) is highlighting either the lack of particle or the casual-ness of the language or both as an example of improper communication (especially coming from a teacher).
dropping particles like that is common in speech rather than writing though, so I’m not sure what a search like that tells you
also I’m not convinced that the teacher using casual language in an after school club would be considered inappropriate…
especially given she’s also drinking in front of them. If anything I think it’s more suprising she’s bothering with polite language at all 
Edit: Couple more points:
Yeah, I agree. I figured it could indicate what is considered to be the most “proper” speech. Dropping particles may be common, but it may not always be considered professional to do so, even in speech.
Like how in English schools, teachers will correct things that are commonly said but not considered “correct”. In my experience, I was told to stop saying “can’t” and say “cannot” a lot. Or things like
student: Can I go to the restroom?
teacher: I don’t know, can you?
So the context of her being a teacher + talking about good communication skills, I could see why the author may have wanted to highlight the missing particle in that situation. Not that it’s inappropriate (because, like you said, they are certainly not in a classroom setting haha), but that it’s funny given the context of who is saying what.
Edit in response to your edit! Yeah, using (?) instead of ◯ is weird. I can’t wrap my head around that. コミュ力 doesn’t seem like an unusual word, so I’m not sure why she would be doubting it.
whuuut? all my teachers used the contractions
I dunno, they probably would have just gone ahead and used a wrong particle right?
先生はコミュ力全然高くないですね。。。
Poor まじめ！ And she’s supposed to be the one with コミュ力.
In typical fashion the “conversation” between すみだ and 先生 had me dying.
Also, having seen the first picture in chapter 13 I could not be more excited for next week’s reading!
Same here 
Their little smiles after their back and forth were too adorable
Love the dream sequence at the end of the chapter! Agree chapter 13 looks interesting…
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That was short and sweet! So as far as I can see the two new girls look exactly like Chito and Yūri from girl’s last tour. Actually the Yūri look alike turns out not to be a new character but we already saw her briefly working in the コンビニ in the first volume. Apart from their physical appearances (and their close friendship) I didn’t see anything else that connected them to Chito and Yūri, although I’m still only on volume 2 of that manga so there might be a connection to later events.
