OOC: Many of the students you've encountered are young - 14 or 15 seems to be the average starting age, but a few are as young as 12. However, you have learned in the course of the day that 16 is the minimum age to enter either of the Queens special services, as well as the minimum age to begin the journeyman stage in training to become Gléas Ceoil.
Students as old as 35 are not uncommon, and the oldest ever to pass through the school was 63 - Marcán Morann became Mharcaíochta and rode posts for the Queen until he died at 81. He fell from his horse, Treasa, and broke his neck during the war to settle Trócaire.