@gmhh i honestly forgot the requirement for the royal class to stay, is it rank 4 or rank 3? Anyway, the one that truly needs to rank up is elizabeta, as she is "the only one" who is still at rank 2
Her other classmates are already at least rank 3 (clara, jazz, caim, sabnock, etc) and rank 4 (iruma, asmodeus, lied, etc)
Ah yes, allocer is at rank 3, IIRC he gets the rank up for his achievement as having the best score in his year during the final test before vacation
Anyway, there is still other activities for them to raise the rank. The requirements state that the have to be at least rank 3/4 (again, i forgot) before they enter the second year. This means that there is still around 6 months or so