Schools (at least in theory) are meant to teach proper grammar to best communicate their thoughts to the world at large, not just their social circle. Without it then speaking and writing can be very unclear, and the person can come off to employers, professors, and the like as unclear. For example:
"Miley told her neighbor that she had had intimate relations once with her boyfriend." Who had the intimate relations, Miley or the neighbor? And whose boyfriend participated, Miley's or her neighbor's? If Miley is the intended referent of one of these pronouns but not the other, the subsequent exchange between them may reach Jerry Springer levels! :tongue:
In theory schools are supposed to teach how to communicate clearly so that they can enter into a good college (granted, many high school graduates have to take "bone head courses" to enter, that is to say remedial high school) or land a good job, not just simply read a menu or have a basic idea of how to speak. It's also important for reading comprehension and learning how to diagram sentences which can help you figure out what someone is saying or even if it's just gibberish.
Even worse, turning words into fuzzy, adaptable tools instead of precision instruments allow for "Humpty Dumpty philosophy" of words (whatever the speaker wants it to mean at that moment, say calling someone who eats meat a vegetarian :tongue: ) as well as enabling spin doctors (and like when Clinton said, "It depends upon what the meaning of the word 'is' is. If the—if he—if 'is' means is and never has been, that is not—that is one thing. If it means there is none, that was a completely true statement"), both of which can easily create misunderstandings, corrupt our politics, and even demean language itself which is the very glue that holds civilization together.
More:
https://www.mtholyoke.edu/acad/intrel/orwell46.htm
Sorry to get melodramatic, and given how mentally exhausted I am right now I'm sure I'm not expressing myself too well either, but kids are SUPPOSED to learn the proper ways to communicate. That's not to say they need to talk that way all the time (though it might be funny if they did
), and I'm not against the use of text speech and the like, just that when it's time to use English correctly then they need to know how, just like one needs to know how to dress for a job interview (while not dressing like that most of the time). Otherwise you might as well leave the kids with babysitters because they certainly don't need school just to figure out how to talk in general, and I'm sure most kids could at least figure out how to read a menu or simple instructions without an education, too.