If you are not a particularly good speller, the more spelling rules you know and understand, the better your spelling becomes because it gives you a framework to determine the most likely spelling of a word and this is supported by a growing body of research (see the references below). Yes, there are exceptions to most of the rules, but around 85% of words are consistent with the rules.
You probably remember this rule from your primary school days: ‘e’ goes away when ‘ing’ comes to stay. However, like many of the rules that are taught, this is only half of the rule. The rule is actually: ‘e’ goes away when ‘ing’ comes to stay or any other suffix beginning with a vowel. Click on the picture to view a video clip of the rule. If students understand the whole rule, then it makes sense that you would retain the ‘e’ in the word ‘safety’ because the suffix ‘ty’ does not begin with a vowel. Similarly, you would remove the ‘e’ when changing ‘nerve’ to ‘nervous’ because the suffix ‘ous’ begins with a vowel.
In many discussions of rules, you will see rules indicating that if a word ends in ‘e’ you only add ‘d’ to indicate past tense or ‘r’ to indicate a ‘thing that or a person who or when comparing two objects. However, ‘d’ and ‘r’ are not suffixes and meaningless. The suffixes are actually ‘ed’ for past tense and ‘er’ to indicate ‘a thing that or a person who or when comparing two objects’. If you take the word ‘safe’ and you want to add the suffix ‘er’, the ‘e’ from ‘safe’ is removed (because you are adding a suffix beginning with a vowel) and your add ‘er’ not ‘r’ to make ‘safer’. Similarly, if the word is ‘save’, you remove the ‘e’ and add ‘ed’, to make ‘saved’. The letters ‘d’ and ‘r’ are not suffixes and meaningless. I explain it to my students by saying the ‘e’ goes away and then comes back as a part of the suffix being added.
Don’t think that your child has to master all the rules straight away. Begin with the ones that are most frequently used or as they arise in the spelling words that your child is currently learning. The Cracking the ABC Code Rules Rule books and the Cracking the ABC Spelling books provide a comprehensive list of the spelling rules.
However, knowing the rules is not enough. Students also need to be able to apply these rules. A really effective strategy for teaching the rules and checking to see if the rules are understood is to ask students to write nonsense words which require the application of the rules. For example, you could ask the child to write the word ‘splame’ and then ask them to add the suffix ‘ing’ or ‘ly’ to make ‘splaming’ or ‘splamely’. By using nonsense words, you know that the student is actually applying the rule, whereas if you ask students to write a read word they may write it correctly because they happen to know how to spell the word rather than because they understand and are applying the spelling rule.
Kemp, N., Parrila, R.K., & Kirby, J.R. (2009). Phonological and orthographic spelling in high-functioning adult dyslexics. Dyslexia, 15 (2), 105-128:
Kilpatrick, D.A. (2015). Essentials of Assessing, Preventing and Overcoming Reading Difficulties. John Wiley & Sons : New Jersey.
Pacton, S., Foulin, J. N., Casalis, S., & Treiman, R. (2013). Children benefit from morphological relatedness when they learn to spell new words. Frontiers in Psychology, 4, 696.