It may be just me but when it comes to stuff like vibrators & such, I can't seem to find them erotic in a classroom setting & it's not only because it's all been done before. Perhaps a reason is that in such a place they seem to become too impersonal (which is why they should only be used in an intimate setting) but it's also that after seeing Sophia looking faintly ridiculous with her skirt pulled up, I think it would add to the 'comedy' if she suddenly started jumping &/or writhing around. This would be compounded by the bulk of the class not, (AFAIK), being aware of why. Will they be worried, amused, puzzled, all of the above? Is it sexy?
We're already due to see 'Carer Sophia' in an outfit resembling a "naughty nurse" costume from a sex products catalogue, or a badly done British '70s 'porn' film in the first side job. That's enough 'comedy' for me, to be going on with.
No 'equipment' would IMO be a good policy for the blackmail route.