Re: If you use or have used Head of the Class...?
For History I use www.lessonpathways.com I like the program and it is free. You can either assign a full planned year or one "stepping stone" at a time. I chose to assign all of the years from 1st through 5th for history and then arrange them in the order I wanted to teach them and I teach both of my boys together. I just sort of adjust my expectations based on age. I was not interested in the K history because it was more of a social studies based on community but if you have a very young student it would be a good introduction to the calender, communities and that sort of thing.
For science you can use lesson pathways as well or I use http://www.eequalsmcq.com/ClassicScienceLife.htm This year. It is a nice program, well laid out and easy to use. The first book is free and my kids are loving it.