Here are some useful websites you can use to help you practise any skills you need to with your maths.
http://www.bbc.co.uk/schools/ks2bitesize/maths/practise all three areas (Number, Handling Data and Shape & Measures)
http://www.crickweb.co.uk/ks2numeracy.html tables, division, fractions and decimals
For mixed practice, try the IXL website (https://uk.ixl.com/math/year-6 for maths and https://uk.ixl.com/ela/year-6 for English). You can choose the objectives you need most help with. You can do a number of questions free each day without having to register.