One of the best ways to help your child develop skills in writing, vocabulary and comprehension for SATs and the 11+ exam is to make sure that they read consistently everyday for 15-30 minutes.
Reading - the key to great vocab and sentence structure
Here's my Top 25 reads that should be on every child's shelf.
I've put together a reading list full of classics and more recently written fiction that I've found are always the hot classroom favourites at reading time. What's more, they are titles with challenging vocabulary that will grow your child's skills in every aspect of English.
Although many parents stop reading with their child when they become fluent, it's important to keep up the one to one support to help their comprehension develop. You can do this by modelling your own comprehension, asking questions, making predictions and most importantly, making reading a fun activity. The Content Domain for the 2014 National Curriculum KS2 reading can help guide you towards the skills your child will need for their Year 6 SATs exams and to some extent, the 11+ exams for grammar school entry.
However, the best gift you can give your child is a love of books so allow them downtime from the heavier classics with books that they can read for enjoyment as well. For this, I would recommend books by Andy Stanton, Dave Pilkey, any of the Horowitz Diamond Brothers books and of course, David Walliams. You'll probably enjoy reading these with them too.