It depends if your staff and students have individual accounts or not. Primary schools often use shared class accounts which I would say warrants Office 2021 to installed on the shared machines. Otherwise, Office 365 is the way to go.
I'm curious as well. We are currently exploring Azure and to be honest, we're struggling to think of what to move there first without "doing it for the sake of it".
We're finding a good goal to aim for whilst planning for the next 3 years is aiming to reach the "standard" that the DFE recommened. A bit of chuckle to read but gives us ideas on how to develop our network.
https://www.gov.uk/guidance/meeting-digital-and-technology-standards-in-schools-and-colleges