Here's another get-up-and-move grammar activity for secondary students!
In this activity, students create sentences by pairing with a partner. One student has a "subject" card; the other has an "object of the preposition" card. After creating sentences, I had students share out sentences that "sounded wrong" while I recorded those on the board. We held a discussion to find the pattern: singular subject and plural objects or vice versa resulted in "wrong" but grammatically correct sentences!