First, it’s not your only rule. Don’t you want students to come prepared? On time? Without candy and gum?
Second, the word respect itself can be open to interpretation. Does it mean “No cursing”? “Don’t interrupt”? “Don’t smack your lips and curse under your breath when your teacher reminds you not to interrupt”? Respect is important in a classroom, but you will also need concrete, specific rules that are easy to enforce.