I think that involved parents do make a difference in a child's performance. But I think the method of parental involvement may be different for each child/student. For instance, sitting with my son while he does his homework is a recipe for disaster. There are temper tantrums, procrastination and way too many distractions. However, DS knows that we are available if he has questions, needs help or (after his work is finished) wants to discuss it greater detail. He is also aware that we will give him a rope just long enough to hang himself when it comes to school work. He is 11 and wants to show that he is becoming a bit more independent. So our rule is that as long as his grades stay reasonable(A's and B's unless he has been upfront and working on whatever is giving him trouble), we will not double check every homework assignment. In reality, he asks us to check certain classes regularly and seems happier now that it is his decision. And his grades are actually better than before.
I don't see that having the parent sign an agenda book each night promotes much parental involvement, which is what our school required through Elementary school.
