There's a note on a couple of the author's other series that they share a universe — specifically, the girls from
Idol no Akahon appear, as successful idols, in
Seitokai Yakuindomo.
But this manga takes place in the same world as those as well! Flashback strips show that Shino, the Student Council President from SYD, was also the Student Council President in her elementary school, and her vice-president was Amano, the class rep/childhood friend in this series.
(I think this series takes place before SYD, as everyone here is in middle school, and I'm pretty sure that Amano is in high school by the time she shows up for her single present-day appearance in SYD.)