Here are some useful websites to practice key skills:

https://sso.prodigygame.com/game/start?rid=c9ab56b5-c2d7-41e6-85df-5d5aec16b791

http://www.primarygames.com/math/grade/grade4-math-games.php

http://www.coolmath4kids.com/

http://www.topmarks.co.uk/maths-games/7-11-years/fractions-and-decimals

http://www.primarygames.co.uk/

http://www.mathschamps.co.uk/games7-9  and  http://uk.ixl.com/

http://www.topmarks.co.uk/maths-games/hit-the-button 

https://nrich.maths.org/

https://www.timestables.co.uk/

https://mathsframe.co.uk/