This is very common in many households I'm sure! - no doubt we are all trying our best to ensure our dd or ds are best prepared for the tests. Many times I have read that children are doing poorly in the tests at home but on the day all the prep work comes back to them and they overcome their fears and succeed - I understand of course the opposite can happen too - but with the amount of effort that people are taking on these forums, its clear that we are making all the effort we can.
My dd seems to have a similar problem - when she attemps a paper, she seems to find the papers which on this forum are deemed to be easy really hard and vice versa with the hard ones, she seems to sail through! so it really depends on what we will get on the day
I do feel that I too am on a roller coaster of stress - but this forum comes in handy to help steady some of the fears and all is not lost.
Good luck and best wishes to you and your son