I said something similar to a class of adults years ago, where half of them refused to participate, follow along, or do anything. The gist was, if you think you can come here, sit and do nothing, and at the end of the year know English, don’t waste your money. Seriously. Because at year end I just knew I will get the blame for them learning nothing.
They all nodded along and then continued to do nothing. In retrospect I should have said nothing. But it is frustrating when you know people are wasting money and will get zero out of it. And the teacher feels useless too.