It might be worth seeing an educational psychologist and having an IQ test to get an idea of his areas of strength and relative difficulties and advice on methods of dealing with life in the classroom (and on whether, eg, seeing an occupational therapist or other professional might also bring some further advice).
Of course, the same issue can be viewed in various ways. For example, problems with getting homework copied off the board in time and with getting straight down to doing what you've been asked could be seen as issues of attention (of which there are various types, including, eg, not focusing on the main point in question, but getting too easily distracted by the details or by peripheral issues (or what "normal" people may view as irrelevant or unimportant but which the person in question may one day be able to prove to have been relevant after all, because their brain wouldn't let them discount it...)), slow processing speeds, difficulties with working memory, issues with auditory processing, issues with visual perception, issues with motor skills, problems with eye tracking, etc, etc. And sometimes it could be a mixture of all those things, but different experts will, of course, put a different slant on things and which is the most important... And then there's the viewpoint that the problem in reality is with the narrow bands of tolerance for different ways of working and thinking that are acceptable within the education system, but since all children have to go through the system as it is at the moment, that doesn't really help their plight a huge amount.
Are your ds's problems a complete surprise to you, or were there indications at primary school of possible issues for the future? eg did they comment on his slow handwriting, or a dreamy, disorganised nature, etc, etc??? It would seem odd that secondary school would create previously non-existent issues, rather than exacerbating them. Bullying and general unhappiness at school could, obviously, make any difficulties far more marked, of course, and secondary school generally, with the bigger space to move around, different teachers and lots of new children to get to know, always makes problems more marked, particularly at first - sometimes creating problems that later die down to the level of being minor issues that the person is aware of and can compensate for without much in the way of extra assistance, but other times making the person aware that they do operate differently from their peers and always will and maybe need some help dealing with that.
Would learning to touch type and being allowed to type a lot of his work help your ds, do you think? It might help take some of his attention away from the physical process of forming the words, if his writing is physically laboured, and free up more of his brain to think about the content more quickly.
My db was in some ways like this - often in trouble at school for not copying his homework off the board quickly enough; not always seeming to listen to what he was supposed to be doing; messy presentation of written work; not just getting on with things; apparently not being very good at standing up to so-called "friends'" bullying behaviour... His teachers found him immensely frustrating, because he was clearly very bright and an original thinker, was capable of producing fantastic work (eventually), was verbally extremely articulate, so he was generally just accused of laziness. He was popular with the girls, though! He did eventually develop coping mechanisms - he is constantly writing himself lists of reminders of what he is supposed to be doing, for example and updates them throughout the day. And once he left school, he found himself a niche where the focus is on the end result, not on constant proof that you are getting on with things in a particular way, which far better suits his tendency to spend 7/8 of the time prior to a deadline thinking things through and looking things up without showing any of his internal thought processes and the remaining time staying up all night, working furiously on his ideas, drafting and redrafting, experimenting, making things and eventually coming up with something quite unique. He got a 1st in his degree,so at that level his way of thinking and working wasn't an insurmountable obstacle to achievement. That way of working just isn't tolerable in a school, though (or in a lot of professions - you need to find your niche)!!!!! He is happily married with a family of his own, now, btw.
It is good that your ds's school is not just writing your ds off as lazy and is wanting to understand and help him.