@WhimsiCat
I don't think it's necessary for Romantica to have been in class B in the past loop in order for Desir and her to develop a romantic relationship. After all, they were stuck in the shadow world for many years and perhaps they only started interacting there. For instance, Desir developed close relationships in the shadow world in the past loop with other magicians and knights which were likely in class A. But certainly, Romantica being in class B would increase the possibilities for interacting with Desir and help explain how their romantic relationship developed so it's probably true.
However, there's no concept of second or third place in an exam that is completed only by the person who reaches the finish first. And I can't imagine a school that places such importance on the status of nobility would take Romantica, a powerful magician and a noble, pit her against another powerful sword magician noble, and only allow one to pass to class A.
As I understand it, the examinees could either end in class A, class B, or just fail to enroll in either classes. I'm guessing that if the luck of the draw had 4 commoners in an exam group, that only one commoner would be enrolled in class B, while the others would fail to enter the school and no one from that group would go to class A because they don't fulfill the conditions. On the flipside, if an examinee group has 4 nobles who are tier 2 magicians, I'm not sure why they wouldn't all end up in class A unless they prove themselves to be absolutely retarded in the exam (and from the characters from the school council like Professor Pugman, the bar is very low.)
My understanding is basically that if you pass the entrance exam, you go to class A if you're a noble and to class B if you're a commoner. And conveniently, nobles are trained in magic and pass the exam while being at least tier 2 while commoners never have the necessary education nor talent to be tier 2, so that's their way of feigning non discrimination with their criteria.
But clearly, if Ajest went to class A while Romantica was relegated to class B, my understanding is wrong or there's some other circumstance that explains it.
That said, I was also assuming that being in class B is shameful for a noble (and class A was jeering class B by calling them losers already). However, if that is the case, all Romantica needs to do is go back home, wait a year, pass the entrance exam then and this time get in class A and have a worthwhile education at the academy (as it was explained that class B was essentially worthless.) After all, I would be very surprised if the entrance exam could only be passed once.
So yeah, hopefully there will be a satisfying explanation next chapter because right now all I'm thinking is: "But why?"