Here is a website link which has lists of high frequency words that the children should be able to read and spell. You don't need to print them out as you can use them on screen for reading/spelling purposes once you've downloaded them. They should first be able to spell/read the first 100 and then the next 200.
You could even get creative and mix up the letters on paper to create anagrams e.g. hdetsou = shouted.
The children usually love this type of spelling challenge.
The following website has all of the statutory spelling rules on and it lets you play games and view words for each rule/sound.Be sure to click onto Year 3 and 4 to find words appropriate to your child.
The following website has four lovely games to practise spellings on....one is even an anagram one if you havent got the energy to mix up the statutory words yourself :)
The below website is great for learning the Year 3 and 4 statutory spellings (the document with the Year 3/4 statutory spellings can be found at the top of the page)