Harry Potter Headcanon

Headcanon: A few years down the line, when the Ministry has finally caught up with all the damage that Voldemort and his Death Eaters did to the Ministry, Hogwarts First Years will notice something odd. There are much older students being sorted.

These are the Muggleborns whose names were erased in the Purging of the Names. Those who, had Voldemort stayed longer, would never have gotten a chance to realize their full potential as witches and wizards, are now, quite late, finally getting the chance to learn why odd things happen around them, why they always seemed so different.

Although the students, both First Year and up, are confused and anxious about this sudden change, McGonagall gets up in front of the class at the sorting ceremony and tells the students that, like them, these older First Years are just as anxious about their unusual circumstances, and that they are expected to make them feel welcome.

Given time, they'll find that the age difference is not such a hindrance, and that like the eleven year olds that are being sorted, whether the older students are thirteen or sixteen, they too have a vital place in the Wizarding World. Things changed after Voldemort rose and fell for the second time, and they as Witches and Wizards needed to be able to change with the times.