The phonetic system of English is rather complicated and many words don't follow the "rules." It is natural for students to try to extend the "rules" that they have learned to words that they don't yet know how to spell. For example, a student who learns the "long vowel + consonant + silent e" rule will want to spell "break" as "brake." Another example are the suffixes "er, or, and ar" which are all pronounced as "er" (baker, tailor, dollar). The student who is not familiar with the spelling of each word will want to spell them all with "er" because "or" and "ar" are not as commonly used as suffixes and also have different sounds.
