I think you need to step back mom. You're in touch with his teachers on a weekly basis? REally? Do you know that most CEO's and captain of industry, most of our presidnets were not A students? Most well rounded people are C or B students. Most people who run scientific labs and write highly technical reports and search for cures for cancer were A students. Some kids are super driven as students, others as athletes, some would rather hang out with their friends and get decent grades. Every kid is different.
Instead of micro-managing why not set up expectations with highly positve encouragement ("we know you're highly capable and we look forward to seeing how to work this all out") and established consequeces for different grades. Set up a contract. A's get high level privileges, B's get some, C's get a loss of minor privileges, and Ds/Fs result in loss of significant privileges. This has to be administers without drama. He stands or falls based on how he handles his work. If he gets a C ask him to self-administer the consequence - but no yelling, whining, cajoling. If he won't do it then you need to. but again - no yelling, begging, etc.
For example, he loses celll phone rights in the evening for C grades - if he won't hand over the phone to you at 6pm then call the cell phone company and they will set it to turn off at 6 each night. Remeber though that he can still skype so you'll have to address that as well. When my now 16 yr old son got in trouble last year he lost his computer and cell phone. He was a drift for a few days, and mad at us, but he figured out other stuff to do.
As for the learning centers - of course they're going to tell you he's behind - they want you to spend thousands of dollars a year at their center. How's he doing with the state standardized tests? At our HS students are required to take labs for math or english if their test scores come in lower than a certain level. We have a college student tutor my son as needed. Ask around, go to your local library late int he afternoon on a school day - all the college tutors are there with students. They charge way less than those centers and the kids like them better.
My son was the most disorganized kid in the world until around 9th grade. All of the sudden he put his notebooks together, began keeping his assignements on his cell phone calendar, and took responsibility for his grades and school work. My son was a kid who could barely read until 4th grade - he was in all kinds of extra help. In 9th grade he asked if he should apply for the engineering, financial or IT academy at our high school and we talked about the options. Next thing I knew we got a letter in the mail congratulating us for our son's acceptance to the IT academy. He did it himself! He's now finishing 10th grade, he's earned 9 college credits this year and is set up for the next two years for computer tech inthe morning and more IT college classes along with HS english and social studies int he afternoon. He'll graduate from high school after having had a paid IT internship, certified in networking and with a more than a semseter of college credits in IT and engineering. And he didi it all himself. ALl this from a kid who needed me to put his notebook together in middle school. All I had to do was step back, ask questions, coach him, nudge him and administer some consequences along the way.
We also make him do chores around the house and do some volunteer work. He would rather be on skpye playing onling games with his friends than anything else. He'll never be an honor roll student - but he will succeed in life.