I taught a combination class for a year, and for the most part, I'd teach one grade at a time, while the other half was working on seatwork. I did social studies and science together, though, which may be more difficult in a public school with the testing requirements. I did a lot of the language arts together, too, or had kids in leveled groups that sometimes included kids from both grade levels. Will you have an aide at all? The biggest thing was a complete lack of time when I was able to sit down...someone always needed me. Also, use a lot of time at the beginning of the year to train them not to bug you when you're with the other class. I had to teach classroom procedures twice as firmly as I did otherwise.