A lot of my students have been told never to start a sentence with the word "because."
I assume they've been told this because they write so many sentence fragments that start with subordinating conjunctions.
Because the sky is blue.
Because money doesn't grow on trees.
Because I said so.
If you tell students never to begin a sentence with because, you don't get sentence fragments that start with because. That's good.
Unfortunately, if you tell students never to begin a sentence with because, you also don't get any real sentences that start with because, and that's bad:
Because the sky is blue, it makes me cry.
Because money doesn't grow on trees, I am canceling your data plan.
Because I said so is why.
These are all excellent sentences, perfectly legal, and English teachers oughtn't to be ruling them out of bounds. But they have, and it falls to me to enlighten my students as to the acceptability of the word 'because' at the beginning of sentences.
However, trying to explain to a class-full of college freshman that, yes, it is OK to begin a sentence with the word "because," just so long as the because-clause is connected to an independent clause, is hopeless.* They've never heard of clauses, and they've certainly never heard of coordination or subordination. (pdf file) Neither had I when I started teaching the class. Not really.
As far as I can tell, the best way to teach the grammar of writing, which is to say the best way to teach the grammar of the sentence, is to forget about sentences and teach clauses instead. Or, rather, teach the clause first and the sentence second.**
Sentences are made of clauses, so start with clauses!
Starting with clauses works because all clauses have subjects and predicates, which is the essential point you're trying to get across about sentences anyway -- but when you start with clauses you can talk about dependent marker words from the get-go, giving everyone a shot at writing complete sentences that start with because, instead of incomplete sentences that start with because.
P.S. I think the Grumpy Grammarian was Philip Keller's father-in-law. (Unless...I've mixed up Grumpy Grammarian with The Underground Grammarian. Will have to ask Phillip.)
P.P.S. I like Richard Nordquist's way of putting it.
*I'm avoiding the possibility that, in the third example, Because I said so is a dependent clause acting as a noun phrase....as well as the possibility that Because the sky is blue is also a noun phrase....
Math is much easier than grammar, I think.
**Actually, I think the best approach is probably to start with words-and-phrases. Nouns and noun phrases specifically, I'm thinking.