As an infant, for many months, you had been listening to others’ speaking.
Then you started speaking.
Your parents and well wishers listened to your speaking. They provided you with corrections and improvements (feedback). You listened to those corrections and incorporated them into your speaking.
This iteration of “listening-speaking-listening” went on for many years.
When you reached school-age, you were good at listening and speaking your mother tongue. That means, you could handle your language for day-to-day life,the stage to accept reading & writing. Therefore, all your school had to do was to build structure into your language (grammar) & expand your vocabulary.
What do we understand from this?
How Did You Learn Your Mother Tongue?