Welcome to the forum, Alison!
I'm sure you're right to appeal if the head encouraged you to do so, but I think it only fair to warn that the panel may be uneasy about the "3" recommendation. It begs the question "What exactly are the head's reservations?" If good progress has been made during KS2, was this not evident when the recommendations were done (early November?), or is the head saying that there has been a rapid improvement between the date of the recommendation and the date of the headteacher summary sheet? And when she says "aptitude," it begs the question "what sort of aptitude?".
It's very helpful that you've given us as much information as you have - I don't know if you feel able to print the headteacher's comments so that we can see whether the "3" recommendation is satisfactorily explained?
Do the good comments from his Y6 teacher re the core curriculum areas relate to ability or attitude?
It would also be useful to know if you have any non-curriculum evidence of ability, e.g. CAT scores.
he had been full of cold the weekend before the first test and was off school on the Monday. He knew that the first paper wasnâ€™t as good as it could have been because he wasnâ€™t 100%
You're on dangerous ground here - the usual rule of thumb is: if he was fit enough to attend school, he was fit enough. If there was any doubt about his being fit to sit the test, he shouldn't have done so.
For information, Yr 5 proved to be a disappointment because his teacher had prolonged periods of absence which resulted in supply teachers taking the class. Most parents complained because the children did not make much progress and there was a lot of disruption from some members of the class. The HT doesnâ€™t perceive that this would have had an effect on the 11+ scores. We want to keep our sonâ€™s appeal positive so should this be mentioned?
The head is right that one would expect the impact to be most obvious where the curriculum is concerned, but it's worth a mention. His progress in English would have been even better - you might have hoped for a 5a prediction - and you could try arguing that if, as part of that, he had developed a more extensive vocabulary, it would almost certainly have helped him with verbal reasoning. Do you have any proof of the disruption or of parents' complaints?
I'll gladly try to answer your question about year 5 SATs, but could I ask which month they were done? Presumably one of the Maths results is meant to be Reading?