I put together a list of who went to which schools, along with their ages, for easy reference.

[b]Signal[/b]
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Jack, 17, 
Kalimay, 17
Morella, 18
Orion, 19
Reya, 18
Tarkus, 17
Tirren, 16

[b]Lantern[/b]
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Addica, 15

[b]Unclear Which, but Schooled[/b]
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Alistair, 17
Arara (Unnamed Private School), 16
Grizel, 17
Isaac (Unnamed Private Academy), 17
Oliver, 18
Sayuri (Unnamed School in Vacuo), 18 

[b]"Home schooled"[/b]
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Casterly, 17
Daiki, 17
Pascale, 18
Rygar, 18

[b]Unclear[/b]
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Kiora, 17