If you are depending on flight instruction for serious income and plan to eat next month, you had better charge the going rate for the time you spend sitting there doing things to help students learn. I have to admit, it is hard sometimes to keep the clock running while a poor student hears a lecture that often degenerates into minutia. So what you should do is ask the other instructors what they typically charge per week and per lesson, and do the same.

By this argument I am seriously undercharging my students at the flying club I currently work for. Their policy is no charge for ground school. I think this is a ridiculous policy. It what they do and I want to work for them, so I also have to do it by consensus. They all have lucrative jobs and this is a hobby to them. Not good, not professional. I told them they should charge $35 an hour for ALL ground time and they said we don't do that here. False charity. I told them if you do not charge the instructor has no incentive to do anything besides fly, which ultimately costs the student more flight time. I was right, they were wrong... but the majority ruled.

Charge at least $35 an hour for your ground school time and generally include a half hour ground per flight hour or at least per flight lesson. That's a MINIMUM. If you stay longer, the clock runs on. It will reduce flight time thus making it a sound value to students.