Hello, I'm beyond myself with sarcasm and dismay at my position now as an ESL teacher teaching the most horribly stupid genuinely terrible ESl material a country has ever produced. Simply asking for a reference to convince the idiotic school I work in that the superlative of clever is NOT cleverer. DO YOU KNOW ANY REFERENCES? Thank you nice, English speaking people. I love you for the fact that you speak proper English that is music to my ears. I am a product of 9 years of Education in the USA and proud of it. Sorry for being emotional about my question, I just couldn't help it. BTW, the stupid lesson before this one amusingly suggests to 9th graders that in the "funky" future we will eat pills and that babies will be cradled and fed milk by an "ELECTRONIC CRADLE". How messed up is that? Crack? Most probably.

Cleverer is the comparative form, indicating a relationship between two subjects, i.e., "Jane is the cleverer of the two." Cleverest is the superlative form, which indicates a relationship between more than two subjects, i.e., "Jane is the cleverest of the group." Any respectable English grammar handbook should address this issue, but I provided some links below, just in case a handbook wasn't readily accessible.