Mr. Schidtler asked the class for a sentence containing the word "dismissed" (which was correctly spelled on the chalkboard). Kevin Sommers suggested "Class dismissed." Mr. Schidtler admonished him because he "left out the preposition and the verb", suggesting "The class is dismissed" as a valid sentence. But "the" is an article, not a preposition. Even so, prepositions include over, under, and through. A pronoun, such as my, our, or this, would be a better fit than a preposition.