The following link is to the 'Essential Lists' as found in the Spell-Write Dictionary.
A guide for parents to follow is that by the end of Y2 children should be expected to know all the words in List 1-2.
By the end of Y4 - Lists 1-4
By the end of Y6 - Lists 1-6
By the end of Y8 - Lists 1-7
In some cases children will have mastered all these words at an earlier stage. There are lots of other words your children could learn too (surname, family members' names, places, days of the week etc).
The spelling lists we send home are these Essential Lists broken down into more manageable lists. Please feel free to help your child learn the other words on the list and to practise spelling words on earlier lists