Hi, I don't live in your area, but hopefully someone will post you some more specific advice soon who does
I have a ds who is also in yr 4 and have a yr 6 boy who will be going to grammar in September. Your son sounds like both of mine who are reluctant to put in any effort but I know they have that extra something about them and are bright even if at times they don't seem particularly academic.If he loves reading, thats great and yr 4 is still quite early, I think to tell which way they are going....my ds1 wasn't thought " historically to be capable of passing the 11 plus " but did really well.They do need some tutoring, it isn't fair otherwise...you wouldn't attempt to pass your driving test without learning a few things, would you ?!
I'm afraid I'm not up on the cats , but I'm sure someone can advise you/ explain them. Have you tried any workbooks etc at home with your ds ? That might give you an idea where he is ?
Is the comp very unsuitable ? Sometimes it's best to look round and you may be pleasantly surprised ? However on the other hand there is nothing wrong with aiming high and wanting the very best....I think if you help and support your son, you should just go for it !
Probably not much help....just felt you needed at least one reply !