How do I get my DS (just finished Y2) to write at length & with speed?

[eemum]

Really in need of help. My son has just finished Y2 & got Level 3s in all his SATs, except for writing where he got 2b. This is no surprise as all year his teacher has constantly had to ask him to write more & he often struggles to finish written pieces in time in class.
His reading is great, his ideas, spelling, punctuation & handwriting are good but he just doesn't write enough - and hates doing it. Am really worried that this will start to impact on his success generally, as he moves up & is expected to write longer pieces in other subjects & later when he will be tested under time constraints. We have tried all sorts of things at home to encourage him - trying to make it fun - but this is a child who has to be cajoled into writing his christmas wish list!! Feel like I've failed him by not finding the right way to develop his enthusiasm when he is otherwise a very capable & keen learner.... Anyone had similar experiences with their own child or one they have taught?

eemum my DS is eaxctly the same.
We have the problem that DS is fundamentally lazy and dislikes work - this means anything he has to work at or try hard gets left behind. He too has good language skills and can make up the most trmandous stories but will not write it down. i was getting hung up on it but as another has said level 2b is average for the country so you shouldn't give him a hard time for being average. All I said to Ds was that, as he belives himself to be very bright - no self esteem problems there - that he had done very well in his other subjects and he got an avarage grade that an average person would get for his handwriting - he still doesn't like writing but he's making less of a fuss when i have been asking him to practise a bit!!!

DD all 3s except writing, which was a 2a, shes not lazy, a daydreamer or anything else really but spends a disproportionate amount of time thinking and planning what to write than actually writing. Since she is not 7 until end of August we are just leaving her alone and praising her when she does write. Poems, riddles, songs are all ok - stories just a little short!!!