If your school is at the side of a road, ask a few children to collect a list of number plates. List about 20 on the board and give the children several minutes in which to invent three-word sentences from them.
For instance, one of my old bangers was MNJ 621. This might produce the sentences "Mice Never Joke" or "Mervin Noticed Jemima". Dictionaries are very helpful - and it may be worth drawing their attention to the idea that often the middle word will be a verb.
Another way to play the game is to select one three-letter plate such as STP. Then brainstorm verbs that start with 't': took, tied, tried, tickled, toasted, tortured. Now list nouns that start with 's' and 'p', such as sand, space, silence, sun, sandwich, situation and primroses, pears, party, purpose, polite. Go on to create simple three-word sentences, such as "Sun Tickled Primroses". Let them add in any useful "small" words - "The Sun Tickled the Primroses''. For the third word, adverbs can help - "The Sandwich Tortured Politely"
Pie Corbett is a literacy consultant