Some teachers ban all contractions because they want students to write formal prose. Contractions are indeed slightly informal, but academic writing doesn’t demand such a high level of formality.
Contractions are perfectly acceptable in all but the most formal writing: amendments to the constitution, declarations of war, invitations to royal weddings, and so on. Academic authors, whether of scholarly articles or classroom essays, can and frequently do employ contractions in their writing. Hysterics from misinformed English teachers won’t ever change this fact.
First-Rate Writers Use Contractions
— Stanley Fish, Is There a Text in This Class? (311)
“Where questions of style and exposition are concerned I try to follow a simple maxim: if you can’t say it clearly, you don’t understand it yourself.”
— John Searle, Intentionality (x)
“His argumentative strategy is totally brilliant and totally sneaky, and part of both qualities is that it usually doesn’t seem like there’s even an argument going on at all.”
— David Foster Wallace, Consider the Lobster and Other Essays (98)
“What they forgot is that the working classes didn’t want to read them.”
— Jeanette Winterson, Art Objects (41)