My daughter also sat the test for Camp Hill recently and I believe that the test for children who were absent is different. I have no idea how they standardise these tests across the two groups of children. I think some parents believe that doing the test late gives them an advantage (I have heard through gossip and rumour). I don't know why this is. The University of Durham believe that they have it all sorted through their reliability testing. They test the reliability of all of their tests through sampling results from groups of children and then analysing the results statistically - they should reflect the normal distribution. Of course, statistically it will be reliable in the same way that any external test should be reliable. It is that same as comparing GCSE results across two years - each test should be equally as difficult, but often we say at school - Oh, that was a good paper. It depends what you are good at.
However, on a more reassuring note, my other child is already at Camp Hill and everyone that I know in her year and other children who I know at the school and at Five Ways and Handsworth, sat the test on the day.
I think it may be more stressful for children to sit late, as they will have heard from friends how terrible the test was, or how easy it was (then they find it difficult!).
The wait is awful - the Foundation probably already know if your son is going to the school, but they can't tell you. My daughter started in the year that they changed the system of admission and we were all geared up for our letter on 14 Feb. We then got a letter from the Foundation saying, sorry the council hasn't got its act together - we know the results, but we can't tell you for another 2 weeks. Talk about stress.