You are right about some language schools charging high rents. I own a space that was rented to "COINED" language school. They marked the rents up a lot. Their shell company (last I heared "COINED" is just a name invented for internet, which is legal) still owes me rent from 2012. The director of COINED, who´s also the director of the shell company, lost his case to avoid paying rent, lost both appeals and my lawyer says the shell companie´s in the process of being put into bankruptcy.
Be careful about dealing with such companies !