We aren't starting formal school for him at just 4 years old but he very much wants to be like the big kids so we got a couple workbooks for him to do "school" in. It's good exposure to begin tracing letters and practicing sounds. When he tires of that he heads over to the busy bins.
Em loves her desk and loves writing and workbooks. She is quite the reader and I try to make sure that she has lots of quality books around to read.
Look at the little lefty. Can't you just see those wheels turning?