My point in separating between NS, MM, and SI from the novel characters was for a reason, y'know. XD I would say, have Neal Samson, Miharu Mizushima, Satoshi Ichihara be 17 instead.
20: Kyusu "Kasey" Kanbai Arashi
19:
18: Cynthia ??? Lumina, Xavier Damien Lumina
17: Angel Divina Boski, Samuel "Sam" Edgar Pearsynn, Rosalina "Rose" Katniss Starke, Lydia Aqua Lumina, Kathryn "Kate" Cora Lumina, Neal Samson, Miharu Mizushima, Satoshi Ichihara
16: Krystal ??? Kollyns, Destiny Delilah Saviouer, Dimitri Ulric Zraen, Damian ??? Drikzen, Luna Cynthia Krescent, Solissa Eloise Krescent, Zorya Bellatrix Solistum, Ethan Storm Lumina, Fira Lumen, Riley Davids, Daniel "Danny" Avery, Lawrence Justice, Rubi Boudreau
15: Shun Yuuto Sorukei, Cornelius "Nel" Jethro Young, Raishuma "Rai" Sutkuro Arashi, Brent Mason Xiore, Lilith "Lily" Camille Lumina, Lucille "Lucy" Cecelia Lumina, Bai Kong
14: Kristopher "Kris" ??? Kollyns, Blaze Jerome Raven, Cole Vladimir Starke, Dustin Adam Glaas, Sierra Kirsi Silverstein, Sainan "Sai" Chuiseishu Arashi, Lucas "Luke" Lysander Lumina, Soo-yun Lee
13:
12: Sarah Lilah Lumina
11:
10:
9: Farah Christine Starke
Unless 17+ is strictly for teachers. XD Then, make each person from my characters younger by one year (Neal Samson, Miharu Mizushima, Satoshi Ichihara 16, Novel characters 15, Bai 14, Soo-yun 13)