My non O expires in mid November, the day before it expires I plan to exit and re-enter extending my stay for a further 90 days.

I'm volunteering at a gov school, and we have been talking about me staying throughout next years school terms.

So I'm looking at extending my current visa (I guess), 1st question, do I request the extension before the November expiry date, or during the 90 days I have on my final entry?

As it stands I'm not sure if the school will make a volunteer request for extension or a work permit request. Can the school sponsor/request the extension based on volunteering? The school is not the organization that requested my current visa. Thx

You do not have to wait for your visa to expire to do an extension. You can do it during the last 30 days of the 90 day permit to stay you get from it. You are extending your permit to stay not your visa.

It does not matter who sponsored your visa.

They should first apply for the work permit and then you can do the extension. Perhaps start pushing them now for the work permit so that there is no delay in getting the extension.

You can do an entry form you your visa up to the date it expires and get another entry.