This is a fun visual strategy to work on vocabulary development. The size of a child's vocabulary has been shown to be related to their reading proficiency. It makes sense that children who have a lot of words in their repertoire face fewer challenges, since fewer words are unfamiliar.

To make your own, you will need some window markers or window paint and some challenging reading materials. Books don't have to be beyond your child's reading level; they just need to have new and unfamiliar words that you can encounter together.  Try adding the most challenging to pronounce, words that your child wants to see spelled out, or words that your child thinks are fun to use. Try using the words in conversation at home. And, as the window fills up, wipe off words that have been established in your child's vocabulary and use the space to add new ones.