I'm afraid I don't know anything from before last year when our eldest took the test. His brother has had better scores this year but it is down to ability and willingness to do practise papers plus a little more parental knowledge about how things worked.
The first didn't see the point, thought he would get in to Crypt which was the only one he wanted to go to and it wasn't until we took him to one of the non-grammars in Gloucester that he realised he'd better try harder... He made it to Crypt but only just!
Second son this year did some of his brothers practise papers last year almost as well as his brother so we didn't have too much concern especially as he is a late birthday so that could only help. In August we bought some papers and he worked through them 1-2 a week, our input was to mark and point out silly mistakes of which there were plenty. In fact during the last few months I've realised just how little patience I have so his father was in charge of marking!
We took a very laid back approach with both though whether that was down to laziness I wouldn't like to say.
We had no choice about tutoring due to costs but had that been an option we probably would have gone down that route 'just in case'. We consider ourselves lucky to have both at/going to Grammar schools but can't really claim any credit other than to encourage.
Oh and a little tip, watching Countdown definitely helped our youngest with his maths, he watched it nearly every day last year and his maths ability shot up.