Mr. Smith is on a field trip with a group of high school EH students. One the way they stop at a fast food restaurant for lunch, and Warren and Raul get into a disagreement. After some heated words, Warren stalks out of the restaurant and refuses to return to the group. He leaves the parking lot, continues walking away from the group, and ignores Mr. Smith's directions to come back. What would be the best course of action for Mr. Smith?