He says he gets bored, has he done the test at school to show what level of education he is? My mate's sister rebelled from boredom and turns out she was super smart and school wasn't wearing her out/challenging her. Other possible tests are ADHD as previously mentioned or dyslexia? Also have you tried getting him say painting stuff/sketching stuff? might need a creative outlet.

Good work on the diciplining though, better sooner then later and you may feel like the evil stepmother but you're doing the right thing
this is it he is a very smart kid, in top 10% for maths and reading and spelling.
his creative writing is the only bit that lets him down.

we try and engage him in more complex things and give him harder puzzles etc to do.
i try and encourage him to draw and do crafty stuff with me, but he gets cranky if i set rules on it, like keep the stuff on the kitchen table and not the walls lol.

i have thought of ADHD a few times, just with his mood swings and outbursts.
but so unsure..

his school work, does get left behind and he often tells us he gets bored at school as he has finished his work. and i agree he isnt being challanged enough at school but in a composite class its hard.