Reading and spelling
The English language has a misplaced reputation as a very irregular language. In fact it is 85% regular. Some sounds and symbols have a one-to-one correspondence, while others are rules-based. History plays a role. Most of the irregular words come from the Anglo Saxons, who gave us English words such as child, post, she, and they - very common everyday words.
It wasn’t until the Vikings arrived and conquered England that we got suffix –s for plurals, which explains why we say goose and geese, child and children, sheep which is singular and plural.
Teaching the rules and the history takes out the need for guessing, which is often the primary strategy for many of these students. This provides them with a framework that makes sense to them. The rules are applied to reading and spelling, and each reinforces the other.