Glad you’re liking the plugins, Vince 🙂
That’s an interesting scenario. Potentially you could use something like WooCommerce Tickets or EDD Tickets and have teachers create free tickets for events – the resulting “order” could then be approved or declined accordingly. Though it’s bending the purpose somewhat, there’s no reason you can’t do something creative there as it sounds like, from a high level, that’s basically the kind of flow you need.
I’m not sure if you anticipate teachers having admin access with which to create events/tickets or not – but if not possibly you could also make use of Community Events. Out of the box it doesn’t let people set up tickets in their submissions, but you certainly could customize it further.
…Or… you could follow your own path and do something completely custom – a lot depends on what you feel comfortable with.
I hope that helps, but let me know if you have any further questions on this one 🙂