I assume all eligible Y6's are doing this on Monday morning? DS will be out late at a music event (arranged way before we knew dates) on the Sunday, so will probably be quite tired on Monday morning.
So, my question is, is this just a reading test, or is it about comprehension and will involve writing too - ie how much concentration will it actually require!? 
There's no way I am going to stop DS from going btw, I just wanted to know what he will have to face the morning after!