Well, buckle up. He's becoming a tween and you're going to have this streak of independence for the next 4 years or so. So, pick your battles NOW and lay the groundwork.
Remember that neurologically, this is the same type and speed of "brain growth" as he had when he was 3..... except that it's coupled with a tsunami of a hormones.
So, remember that your job as a parent is to TEACH him how to behave because his brain and his impulses are fighting a war, and most of the time his brain is 30-45 seconds behind his impulses. So, get more involved with him (I found it to be equal to the invollvement I had when my daughter was 3)..... but at a different level.
He wants to manage his own life? GREAT!!!!!!! Talk him through the consequences, ad nauseum. You don't want to do homework? What will happen if you don't? (let him come up with answers) "that's right you'll flunk" "what will happen if you don't get good grades" (let him come up with answers) "that's right you won't get into college"..... or whatever. Oh, the conversations were AGONIZING. But you have to teach him how to THINK like a man. he won't just learn that on his own.
I stopped using "because mom said you had to" long before now..... and focused on my daughters role as part of a family. Your son needs to understand WHY it's important. Not because he loses a playdate, but because of how it impacts others, makes other see him (lazy, irresponsible etc) and then what the consequences to THAT are.
It's exhausting. WAY more exhausting than what I called the "terroristic threes".
Now is a GREAT time to expand his knowledge of budgeting, how the family household runs etc. Make him a bigger part of the overall unit. Get him involved. Give him things to "own" and be proud of so you can give him TONS of "great job on the yard.... or whatever" and LIMIT the amount of his ability to misbehave or give you attitude.
A busy boy is a boy who doesn't have time to give his parents trouble.
I also second what the other mama's said about his age...... If you haven't had very specific conversations with him about sex, interpersonal relationship, personal hygiene etc with him yet....... start..... like yesterday. My daughter was the VERY youngest in her class (by 2 or 3 months!!!!) and even she had turned 9 by the first day of 4th grade. lots of girls start their period this year and have started wearing bras. Lots of boys and girls think they want to "like" each other. uggggggh.
Don't turn yourself into the enemy. Be on his side.
Get him prepared to be comfortable talking to you about all the chaos that has erupted into his little world..... instead of being frustrated with the fact that he has lost the ability to control himself!!!!!!
Good Luck.