I'd been looking for a way to deepen and extend our Astronomy lessons. We used Apologia's Astronomy and it's worked wonderful for the 4th, 2nd & K -- but the 6th grader had already absorbed most of the information from her independent reading. So, I as we progressed through each chapter, I made Montessori cards for her (and the others) to extend the lesson. She colored 6 cards of a sun and then using a diagram I found online, sketched in corona, core, convection zone, etc. I copied the cards so she had duplicates and she can match the picture with the label and match the label with the definition. It helped!  So, I took information from each chapter in Exploring Creation with Astronomy and made more cards.