The ecchi is more subdued and make more sense in-universe than in other shows.
Miss Caretaker is delightfully aware of what she's meant to be, visually, and her...playing up that role is explained so easily by the context of her interactions with Akkun.
And, further, the other girls' T&A time can be explained as a means of comparison--both to Akkun and the Prez.
Akkun's whole deal is his desperation to be seen as manly because he's so undeveloped (in terms of his male features, probably having to do with--if reality is allowed its due at all--his not hitting puberty, fully, yet), and that lack of physical maturity is contrasted both with the (general) maturity of his demeanor and with the HIGHLY developed (perhaps overdeveloped) physiques of the girls surrounding him. That is, they make him seem (physically) less mature AND play up his inability to properly process their prominent sexuality--in terms of his reactions and, I think, their...exaggerated features being at least half-owing to
his perception of their appearance rather than an accurate representation thereof--which also makes him seem less mature.
It's all basically the same for the Prez, with a lot of emphasis on the sight gag of her standing next to the other girls, but also a real focus on how her perception of her body is a hurdle to properly expressing her feelings about Akkun: how could she ever dream of doing such a thing when she's constantly up against Sex in a Sweater?