My DD was successful in 2009's Kent assessment and has secured a place in our first choice school.
We were not led to believe by the primary school that she would be suitable for 11+ and she was behind in her KS Maths. So at the beginning of yr five we started looking for a tutor and was shocked to realise that most were full, however, we found one who was excellent and was connected to local education and had good Knowledge regarding the local test requirements, (expensive though Â£32 ph). Within six months of one hour weekly tutoring and with support from us at home, the dynamic changed and she gained in confidence hugely moving up four subsets in one year which was equivalent to two years' learning. It was a confidence issue as she obviously had the innate ability, she just did not believe in herself.
My only word of warning is that she did become a bit complacent towards the exam, she had been told she was able and should pass and that was enough for her- she's not exactly driven! The extended summer holiday last year didn't help either as she simply wouldn't work for us- especially on holiday, ( she can be lazy...). She did exhibit signs of stress though as the exams were only two weeks after the return to school, so I think consistency is key.
Good luck and relax! Not easy I know