In French, negation is typically formed by placing "ne" before the verb and "pas" after it. The sentence "Il fait son devoir à la maison" translates to "He does his homework at home," and to negate it, "ne" and "pas" must be correctly positioned around the verb "fait." Therefore, the correct negation is "Il ne fait pas son devoir à la maison," indicating that he does not do his homework at home.