- Online classes are not a good medium of education.
- Online classes is not a good medium of education.
Given that this is the only context available. I don't know why but I think #2 is correct in this case, since we are probably talking about the concept of “online classes”, but I am not sure since it could also be #1 because of the fact that it has a plural noun, i.e., “online classes”. Which sentence is correct? Also if #2 is correct, should we put online classes in inverted commas?