Teachers are under a lot of pressure to be "tolerant of different means of self-expression." This means, sometimes, not criticizing students for grammar, spelling, illegible handwriting, or other examples of non-conformity.
I can agree with this, to a point. I would hate to see a student pour out his/her heart in impassioned, and well-reasoned, prose, only to have it returned with "You split your infinitives - C+". On the other hand, it is a disservice to students who will have to write professionally not to teach them how to write in an accepted format. Unfortunately, a lot of graduates hit the working world with the attitude "as long as you know what I meant, it's fine."
Isn't there a happy medium? I'm pretty bad at spelling. And my grammar is pretty wonky. And lots not even start on my handwriting ok? But I've always loved to write and I'm pretty good writer. My teachers wouldn't mark me down terribly for spelling or grammar but rather give me tools to help me. Like insisting we always have someone proof read our work (by the way, it's always been my best friend, her writing isn't the best and dang can she spell and she's pretty good with grammar too. She's been proofing my work since grade school), or telling me to slow down, look words up, ect. And I'd get the same with my handwriting, just slow down a little. It's still not great, but it is legible and neat.
I'm not a teacher, nor do I play one on TV (which is good, because they're all twerking with students, or sleeping with students, really TV teachers have gotten quite terrible), but I'd want my pretend child to be able to formulate a decent sentence and also express themselves. I'm pretty sure they aren't mutually exclusive.
Though I did once have a boss who while checking her step-daughters homework, lost it over it being "sloppy" (didn't look too bad to me) and erased everything she'd done and made her re-do it. It was math homework and I guess her numbers were "sloppy", she really tore the poor girl down. So I could see it getting out of hand. Of course boss lady was not a nice person in general. There's an encouraging way to give criticism and a discouraging way. She was all about the discouraging way.
I think if you enjoy writing and do it even as a hobby, you owe it to yourself to improve your spelling and grammar skills.
And I think if you are in or want to be in a professional career where you will need to engage in written communication, it is a must. If the lawyer I'm dealing with can't spell, how can I trust them to know the law?
If you have someone proofing your work, are you reviewing the corrections so you stop making them next time around? Everyone makes mistakes, typos happen, but there's a huge difference in one typo and a letter than reads like a 5th grader wrote it. Take pride in your work and present it in its best light, I say.