Well, poo.
I was okay with most of what happened on my interview the last couple of days: although I'd found some aspects on the second day to be quite stressful but they were happy with what I'd done. I was 98% happy and and just called to check some details. They had told me I'd be doing about 2 days a month working with 13-14 year olds on an "Experience day" doing woodwork. I called today to check about this part of the job, mainly that I was part of a team rather than working on my own with the teenagers.
They've just told me that no, I'd be on my own. With 12-15 teenagers I didn't know and who may or may not want to cooperate. That means I am responsible for their safety (doing woodwork. With very sharp objects everywhere) and everything that happens in the room, and I'm specifically not trained to work with this age group or large groups. I have limited experience with this age range, most of it bad, and none of working in a school situation.
Other than that I'd pretty much decided it was doable and they had seemed to like me.
D*mn, D*mn, and D*mn...
(Edited for spectacular typos)