How can I ensure DS does what he is capable of?

[topbannana]

Can anybody advise please?! :)
DS is 8 years old and an only child and has always been a bright little boy. All his reports say he is clever, a pleasant member of the class etc. (sorry if this sounds like a stealth boast, it honestly isn't!)
At the end of the year we get the years exercise books home and TBH I was quite shocked by the poor standard of most some of the work he has done in school. We always do homework to a high standard so its clear what standard he is capable of when cornered like a rat properly supervised.
He really enjoys school but seems easily distracted and loathe to put in the extra effort that he is capable of. As I said earlier though, his reports are always glowing. Are they therefore generic "good, average or poor" reports that the teachers adapt to suit or is he really capable of greater things?
Anyway today I was decorating his bedroom while he is away, and I came across some stories he has written. The structure and vocabulary is so far removed from what he churns out in lessons it has me slightly worried that he could be selling himself desperately short at school.
So what do I do? Will he mature soon enough that he begins to take responsibility for himself? I am loathe to become any more involved for fear of becoming draconian and him switching off completely (as happened to me)
Also, unsure if it is relevant but he started nursery/ reception in prep school where they were heavily supervised and he thrived. At state school we knew and accepted that this level could not be maintained but do you think this early experience has made him almost lazy when left to his own devices? If so how do we stop it?
Many thanks and apologies for the essay :)

Have you asked him about the difference in standards?

Sounds like one of my sons.Tbh I just bugged the school and insisted they keep on top of it with to begin with a smiley chart in a book he got signed for each lesson and then just at the end of each week after a while .We rewarded(came down on him like a ton of bricks)as appropriate.

We were lucky, teacher very patient with us and him and by the last term he didn't need anything.I still think he sells himself short and has a way to go but his attitude has changed completely,hugely better and he is a different child now.I think it was knowing both school and home were singing from the same hymn sheet and he wasn't going to get away with it.

He hated getting the book signed and I felt slightly(only just) bad as he is well behaved,quiet and polite so it was harsh but we really needed to be kept informed and on top of things.I was worried he'd just slide into falling through the cracks. Also worried as his writing(which he hates,a leftie) was having an impact on other areas of the curriculum he's very good at.

Just hope he keeps it up next year,he's going into a job share which I'm slightly concerned about but they're pretty good from what I hear and his teacher has promised to put them in the picture.

You will become known as the anxious, pushy parent but to be frank it's not a popularity contest and my dc's education will always come first.

mrz its always somebody elses fault! Theres either not enough time, X was talking to him or Y was hiding the pencils and so on
prairie thanks for that, it seems like the way to go TBH. My worry is that he will be starting yr4 in September which is his final year at first school. When he goes to middle school I will be so much more out of the loop as he will get the school bus in (we live quite rurally) so I will not be seeing the teachers on such a regular basis. Also the sheer size and speed of middle school compared to the very small village school he is in currently, means I fear he could just get swallowed up.
So "anxious, pushy parent" it is then :o

Time is an issue in school, often by the time the teacher has done the introduction children have very little time to actually write, especially if schools are following the "literacy hour". At home your son has all the time he wants/needs to complete his writing so this is bound to have a positive effect. Incidentally I'm impressed he is writing at home.

It does sound as if he is distracted (a little or a lot) at school so this might be something worth chatting to his teacher about, sometimes just changing seating arrangements can have a big impact.