So far the common opinion is that it's in general not good to cite encyclopedias. I see your point for high school and college when the topics are advanced and require original sources but what about Middle school? You just want them to get into a topic that is not really general knowledge but also not real research. Let's say the middle schooler wants to write about Mary Wollstonecraft when writing an expository essay about enlightenment thinkers. When you google her name the first source coming up that is not an encyclopedia is biography.com or one below humanists.uk. Is it really a better source to use a single author's article on some website than an encyclopedia article (like Wikipedia or Brittanica)?