I can't speak with any certainty about the "Western World", but I can say that the tradition to have schools begin their session in the autumn (Michaelmas in the UK/Ireland, late September) is older than 100 years.

The linguist/Celticist Osborn Bergin notes an account that details life in the Irish poetic/bardic training schools of the early seventeenth century, (one which arguably also holds sway for the Scottish bardic schools as well.)

...the students upon their first coming, which was always at Michaelmas, and from thence till the 25th of March, during the cold season of the year only, did that close study last. At that time the scholars broke up, and repair'd each to his own county, with an attestation of his behaviour and capacity from the chief professor to those that had sent him.

They also got Saturdays off, and festival days. Bergin compares it to modern university life. That schedule certainly is similar to modern universities today. However, in the case of the poetic schools, I do not know that they necessarily all would have gone home to help with the harvest. These educated men came mostly from families of poets, not farmers. Instead, the harvest (and religious festivals) may have served as a natural cutoff point for the students because so much else in Irish life revolved around it.

Of course, there are plenty examples outside of the Irish/Scottish poetic tradition! But I have absolutely no business talking about them.