If singular they has deep historical precedent, then it is dispositive on the sub-question of what is traditionally correct.[…] Putting the referent in the plural – “All the students aced their projects” – nixes the troublesome (grammatically singular but semantically plural) each student.Read on. You know you want to.
I first heard the singular they on The Archers when I was 12. Someone somewhere in Ambridge had done something wrong and the speaker growled, “When I find out who it was, they’ll be sorry.” Which neatly avoided ascribing a sex to the offender. How useful, how convenient, I thought then and I still do. Avoids all that “he or she” nonsense which the Economist rightly condemns as “ugly and awkward”.