I find that I will help one of my son's more than the other - not because he is struggling, but - because - I know he knows how to do the work and I know he knows how to find the answer. On the few occasions when he's had "enough" - I've helped him. (It's terrible, I know)

Typically, I will sit and be a presence but I will not give answers. I will try to help with concepts and occasionally will tell one of them to take another look at an answer.
Laura - I really liked your article on Ability Grouping. I'm back and forth on the topic, but I appreciated the research findings you provided. Well written - thanks.