So this is set in Korea, but I used the Australian schooling system (I am Australian), not that it comes up in the story but just for reference in case anyone wants to requests more fics like this one.

Year 12 - Woojin and Chan - 17
Year 11 - Minho - 16
Year 10 - Changbin - 15
Year 9 - Hyunjin, Jisung, Felix, and Seungmin - 14
Year 8 - Jeongin - 13

and the pairings are:

Hyunjin x Jisung

Seungmin x I.N

Changbin x Felix