Please, do not feel disheartened! Don’t look at the glass half empty, look at it the half full! And keep telling your DS he can make it if he puts his heart and soul into it! Self confidence is so important for these 11+ exams!
You still have three months ahead for proper practise and maths is easier to work at than English in term of quick improvement (I mean, to improve the vocab of a child, it takes years of reading and months at working on vocab)
. So your DS can make it, God willing!
A sbarnes suggested, try to find your DS’ areas of weakness and work on these during the holidays (in my opinion, without maybe doing too many tests each day, just one or two as the important at the moment is to do some remediation in his weak areas)
. And then, when your DS will be back at school, give maths priority in your everyday work, insisting more on the tests as the remediation should have been done by then. And don’t lose heart; we need sometimes to repeat some lessons times and times again till the penny drops!
Do not forget regular work on the time tables (for examples one test per day with all the tables mixed up, starting from today if you have not yet established such a habit)
; may be his mistakes are also due to some silly calculation mistakes?
I am sure that we regular practise, your DS’ brain will be ‘processing’ information and calculations quickly.