Enable adults to interact in a second language
I love teaching pronunciation in my language lessons and I dare to leave grammar books behind. Having taught mainly German for seven years, I realised that language learners need to be exposed to easily comprehensible "Lego bricks" of spoken language and their multiple ways of how to put them into phrases and questions. It increases the students' ability to speak and understand, and facilitates the tedious learning of grammar rules. That's why I want to promote language teaching based on spoken input, so that the target language will be acquired in a natural and predictable order.
Language capacity is innate!
Every single human being is born with a general set of grammar rules in their mind. These connections based on logic always remain in our mind. However, some rules might not be "used" as they are not applicable for our mother tongue. But: they are there! This "motherboard of grammar rules" helps us to acquire our mother tongue(s). Having "installed" our mother tongue, we struggle to learn a new language, as we always fall back to our first acquired language. Any new languages are automatically compared to this and we feel the need to translate words into our more comfortable mother tongue in order to fully grasp their meaning. What this means is that our mother tongue becomes the base for the second language. We can only understand the German word "Pferd" because we already understand the meaning of "horse". And so now I ask you: How did you come to learn and understand the word "horse" as an infant without being able to read or write? Wouldn't it therefore be better to turn to and trigger our innate sense of grammar rules so that we learn to directly speak and understand our target language?
Acquisition vs. learning
As a child, you acquire your mother tongue subconsciously just because you are exposed to massive sound input. By the age of six, you are able to speak and understand your mother tongue. Imagine a child who hasn't had the chance to go to school. As an adult they will be fully capable of interacting in their mother tongue, despite not knowing how to read or write. However, reading and writing need to be learnt in a conscious way, after we have acquired a base of how to communicate and interact in that language.
To sum up: Speaking and understanding language is acquired, whereas reading and writing is learnt.
For more information on innate grammar rules and the difference between acquisition and learning: