Find a reward for good behavior or doing something right the first time, chocolate milk worked for us or a long time.
Clean out his room, no more toys, extraneous in there, this helped my son immensely, he liked the serenity after we cleaned out everything. He had one bucket of legos, in his closet, and a bookshelf with only books.
Get into a routine, afer school he has his down time, then start homework, dinner, extracurricular , bath, bed
Homework on a timer, 15 minutes on 5 minutes off, although, this never worked for us, one he got started I did not stop the work in progress. All the professionals I dealt with told me to do this.
Taekwondo, gymnastics, swimming, fencing, individual sports, team sports were a recipe for disaster for us.
Chores are a must do and even if it takes all day, but break them down into manageable units.
Bring me all the clothes Now pick all the legos, etc
You will have to sit in the room with him while he does it. THere are times i still get distracted in the kitchen and end up making brownies after washing the pan.
Make him redo chores that are done sloppily
Because I'm the MOM that's why. or Because I said so, or You're best friend's name is Tommy, not Mommy.
Turn off the tv, no tv until the weekend, my son didn't have any tv until he was 17. We didn't get cable.
And there is hope. My son is ADHD. He was such a mess. But in Navy bootcamp he wrote us a letter and thanked us for being his parents, not his friend and teaching him to clean toilets and iron his shirts.