Before designing their own magazines, children are likely to look at examples of real ones. I’ve done this dozens of times. You hand out photocopies of a single magazine, so that you are all looking at the same thing, and you can guide the class through a shared analysis. You can define key terms about a magazine cover (they have straps, puffs and pugs, among other things.) You can talk about the magazine title, the cover imagery, the fonts, the colors, the intended audience. Using a single magazine facilitates this analysis. It created focus. But it might, in the end, mean that pupils are learning about one magazine rather than about how magazines work in general.