They have changed the company who oversee the marking this year. It is being done on the computer and marks uploaded. There are no longer any borderline checks for those children near to the level thresholds.
All in all a farce!
You could ask your child's teacher if they are aware of these problems and whether they intend to check the scripts once they are returned to school. It would be perfectly possible for your child's teacher to check the paper has been marked and added up correctly - althought his is more difficult for the writing as it is more subjective.
I guess if your child achieves what was expected of them then don't worry too much. But if the result is unexpected then I think you would be within your rights to question the school and ask for them to be challenged.