Have you tried to introduce the subject/topic then have them do the work at their own levels? Examplehonics- introduce the main idea then have 4yo work on what s/he is capable of and have 5yo work on what s/he is capable of. Sort of like the bus- stop approach where everyone learns about the same thing but they apply them at their own learning levels. I always teach above my dds learning levels because even though they can't explain to you what you said they still absorb it and surprisingly will recall what you said or taught at a different date. I am not to familiar with Calvert although my husband wanted to use it at first, so this might be a little difficult with this curriculum. Also another idea is that I reserve things to do for the little one or gently suggest ideas of what to do. I have things 'put away' that can only be used during 'school' time- special puzzles, paint w/ water, simple stuff that is easy to clean up.