This book is packed with such great information about all things literacy related. I learned so much and can now use this information to help my students. Do you know why focusing doesn't double the s when adding the suffix? The doubling rule states that in a multisyllabic word if the final syllable ends in 1 consonant, has 1 vowel, and holds the accent then you double the final consonant before adding a suffix. In the case of focus, the accent is on the first syllable, so you don't double the final consonant.