Parents, is your son or daughter struggling in school?

My 12 year old is in the 7th grade and shows no motivation and is very lazy with school work. He is currently getting D's and F's in four of his classes. I know I'm responsible for this, and have tried almost everything I know of to help him. I have taken away things, we set goals and stay on top of his homework and class work. We monitor his activities and nothing is abnormal. He does well for a short stint, as soon as I feel comfortable and confident that he has "caught on" I let go of the reigns and give him space. As soon as I do that... he is back to the same ol' habits. I try and not be to strict, I never liked that approach, but I feel like I may have to be. Any parents with the same issue?