In my kindergarten classroom, I always printed large reproductions of app icons and attached these to my magnetic whiteboard or put into a pocket chart to give students a visual of what apps I wanted them working on at a certain time. I really liked putting them on the magnetic board, so I could also write beside the app any specific instructions (i.e. how many times to that app, what letters or numbers to work on, etc). When I was in Mrs. Elenbaas' room, I noticed she does something similar. It's so simple and easy ... she keeps the apps attached to the top of her whiteboard and drags them onto the main board as she is instructing kids which app to use.