Key stage 3 pupils will already be developing their noun-expanding capabilities. We'll hear them saying "I like that new young teacher" or "that film with a really cool ending". There are two grammatical tools being used here. The first is the most familiar - using adjectives to modify the noun. (The second is also common but perhaps not a familiar expression: modifying a noun with a prepositional phrase - a group of words that begins with a preposition such as with, of, in.) Here we focus on adjectives. Your pupils imagine they witness a crime one morning on the way to school. The police ask them for a statement. They say: "I saw a man break into a car using a brick and take a radio. The man had hair, a coat and trainers". The police are certainly likely to ask them to be a teeny bit more specific. The nouns - "car", "brick", "radio", "hair", "coat" and "trainers" - are short on detail.
But sometimes their creative writing can become over-elaborate because of a frenzied wish to pack as many adjectives as possible around each noun. Then you get writing like this: "the dark, swirling, impenetrable fog hung around the old, menacing, ramshackle house". It's good to see precise use of language, but prose like this quickly becomes cloying and flabby.
Sometimes nouns need expansion, sometimes they don't. The trick is to find the right balance by looking carefully at expert writing. Get the class to take a couple of well-crafted pages and look carefully at the common nouns (nouns other than names).
We picked out all the common nouns in two pages of Harry Potter and the Philosopher's Stone and counted the adjectives: the longest expansion was about food: "the first six fat, juicy, slightly burnt sausages" (five adjectives, including the numeral); and so was: "a large, sticky chocolate cake".
Another noun had three adjectives: "the fierce, wild, shadowy face".
Five had two - eg, "long, thin package", 24 had one, and 71 nouns (yes!) had no adjective at all.
In short, what counts isn't the number of modifying adjectives, but variety. A long expansion has more impact surrounded by unexpanded nouns.