Write well in what sense? Learning to write comprehensive texts? Good calligraphy? Vocabulary? Interesting and engaging writing?

if you can't write well before college nothing you major in will change that. take a writing class and shut the fuck up

English - Composition

Sadly, English Literature and English Creative Writing have pushed all other English majors aside and bastardized the whole concept of majoring in English. Not many school Composition as it's own thing anymore as a result. Or you could just do technical writing courses.

It can't really be taught. Not efficiently, anyway. Read a lot -- I mean a lot. Read novels, essays, short stories, newspaper articles, Wikipedia -- and write often. Keep a diary full of interesting stuff that happens to you. If you want to write fiction then just go ahead and scribble to your heart's content. If you just want to learn to write nonfiction essays etc then, honest to god, arguing with people on websites like this one wouldn't be a bad use of your time. I'm not kidding. Try the politics board. Just make an effort to write well when you do so.

When you read, read whatever you find fun, not what people tell you you're supposed to read. If you really want to read trashy YA novels then, by god, do so. If you don't actually like to read, then there's not much hope for you and you should probably find a different hobby or career.