maths techinques to improve speed/accuracy

[mum-of-three]

I am a DIY mum preparing for maths mainly through AE Books. Can someone tell me what sort of level is it in terms of difficulty? We are considering the Berkshire school for my DS.

I am in great need to teach my DS techniques related to maths fractions, ratio and percentage question in order to improve not only speed but also accuracy. Any suggestions are greatly appreciated.