Ds1 had all this and he turned out to be dyspraxic. 
Only diagnosed at my instigation (at school they just thought he was badly behaved/lazy) at age of 13 by NHS.
It is a combination of slow processing/auditory processing/sensory stuff that makes them tune out in class and appear distracted. Ds1 had a very explicit approach to homework, unless teacher broke down the steps of what they wanted into small chunks (ie bullet points to be answered) he thought he had answered the question in three sentences.
School day is very exhausting for them, they use up all their energy getting through it and trying to organise themselves (which they appear to do in satisfactory manner, no major outbursts or upheavals) and then when they come home they really collapse appear absolutely lazy unmotivated.
Ds1 was very motivated in subjects which he had attention in small groups, ie choir music lessons. He became a wonderful singer and has grade 5 in violin and singing, despite doing very little practice of his violin (although he practises his singing all the time)
Your ds might need help with study skills rather than just telling him to work harder, he also might need an area in which to excel.
Ds was surprisingly badly behaved in subjects he did not understand. For example in art he was always in trouble for disruptive behaviour because essentially he did not know what they were asking him to do or how to do it (very poor spatial skills and motor planning)
Ds is of normal intelligence, gained average GSCES below what he was predicted and is now doing A levels. He is still very much of the dyspraxic profile. He loves Drama although he is shy and diffident. We are still dealing with the difficulties dyspraxia causes him but I think KNOWING he has it, makes us much aware how much he achieves holding it together staying calm and we try to keep the pressure off. Saying that, the art of pushing him that little bit out of his comfort zone (ie we take his phone away at bedtime rather than expecting him to self regulate) we make him join clubs and classes he is at first reluctant to join (only a few mind you) we found him a tutor for A levels, again something he refused at first. We also try to keep calm if he screams and shouts and is overloaded, he apologises immediately because he knows we are on his side. Essentially we give him a bit of leeway. Everyone who meets him comments on how polite he is. His self esteem is extremely important to us, more important than how well he does in exams, but doing well in school is a very big part of their self esteem so you have to work hard to balance the two aspects.
In short, contact the SEN department and discuss your worries with them, and do not assume it is just laziness. Could be undiagnosed dyslexia for example, which is not about just reading, whatever people tell you.