In economics class we have to present our business plans and mine is coding classes (probably a summer camp for kids) and I could talk about how the coding classes would encourage kids to not make non-libre software
I wouldn’t consider being a teacher something similar to business but more like an ONG. I don’t mean to disappoint you or anything. I share the sentiment of ‘evangelization’. Just, perhaps, share the idea with your teacher beforehand. Plan ahead, another comment mentioned dual-license, that could be an interesting take. Same goes for what many platforms do, which is charging for support (e.g. research for Red Hat Enterprise Linux business model). Good luck!
You could also talk about the business aspect of it. It could be dual-license, service for hire, niche part of a process or simply crowdfunding.