Learning to spell helps to cement the connection between the letters and their sounds, and learning high-frequency “sight words” to mastery level improves both reading and writing. 

“The correlation between spelling and reading comprehension is high because both depend on a common denominator: proficiency with language. The more deeply and thoroughly a student knows a word, the more likely he or she is to recognize it, spell it, define it, and use it appropriately in speech and writing.”

Teaching spelling systematically can also dispel the myth that spelling is unpredictable and too confusing for all but those with a natural gift for it , which often happens when a “correct mistakes as they happen” approach is taken. The idea that English is too mixed up to make sense of is a myth perpetuated by lack of instruction and poor teacher preparation. Spelling is not simple, but when people understand its structure, it is perfectly decodable and not limited to people “born to spell” to understand.

Understanding the rules and patterns helps the student who doesn’t intuitively pick them up and enables the teacher to clear up confusion instead of having to resort to “it’s just how it’s spelled.”