there is no way to modify a child s behavior. A child is acting out usually because of problems they are having. "modifying their behavior" is not the answer. finding out why your child, step or not, is feeling the need to be 'bad' will help all involved. There is a real reason the kids are acting out. I have noticed since my SD's mom flaked on everything, including a summer visit, she has become a bit more off balance, i dont blame her. (I caught her sneaking back into the house tonight) But repercussions will happen tomorrow when dad IS AROUND. there is always a reason why we do what we do and these kids are trying to figure their life out. stay far away from these people who can fix your child in a week. I am a firm believer in outward bound, nols and there are other programs that focus on developing a child's strengths and building on their confidence. instead of their weaknesses. Kids need support, not reconditioning.
good luck