I don't agree with swing about attitude. I think the most important thing is to pick your battles and although that might mean some important boundaries (in our house it is respect for teachers, and getting up every morning to go to school however tired or fed up you feel) Ds1 also know the value of an apology. We let a lot of attitude go, and as a result it has considerably reduced, 2 years in, because he feels listened to and a lot of situations don't escalate, even if he initially flares up, or refuses to do things.
My son has dyspraxia. It makes him impulsive and disorganised and he reacts in a very literal way to things. I have a friend whose son (most probably) has ADHD and is making life hell for her, yet she has no diagnosis, and has put all his behaviour down to "attitude", because he is clever and talented, so it cannot be a SN...but it almost certainly is.
14 is a critical age for feeling misunderstood, and needing support as well as boundaries. I have another friend whose son was lazy impatient and reactive at 14, (has NO Sns) but for some reason by 16 he was getting straight A's, and is now heading to uni to do Stem subject; he is still lively and bouncy but that attitude didn't escalate; I think because she always felt she was on his side (compared to my other friend who felt as if her son was determined to destroy her)
we were given advice by dd's school, in a general parenting meeting, that if your child reared up at you like a Cobra, the answer was to retreat, and talk to them when things were calm, rather than argue with them when they were angry and dangerous!
Please investigate the ADHD, don't let it be a lingering suspicion, also check his Vitamin D levels (this is a new bugbear of mine, ds1 was deficient at 25ng/mol, and I think it very much affected his behaviour, made him depressed and irritable)
Decide on a few rules and stick to them, but don't impose too many rules and let a lot of stuff (tidy room, organisation, greed, money running through fingers, homework woes) with a pinch of salt. He is almost certainly disruptive because he has a problem with the work and is concealing it. The most important thing is that he trusts you, and respects you, and other adults. Also read How to Talk So Teens listen by Faber and Mazlish, I found it very valuable in reminding me what not to say.