One of the hardest things to get across to lawyers is that writing for the internet is very different from writing a brief, or even a magazine article. [I use lawyers as an example only because they are the folks I've talked to the most about marketing.]
In his excellent article Web vs. Print: 5 Key Writing Differences, author Tim Morral does a great job explaining how different it is to write for an online source. I'm not going to repeat all of his information, but I want to focus on a few points that are crucial.
SEO is a term used a lot in marketing. Search Engine Optimization is important, because you want a search engine to find your words. However, oftentimes content that is clearly written for search engines comes off sounding robotic.
I had a call a couple of years ago from a young lawyer wanting me to write blogs for her boss, a DUI attorney. We had a lengthy discussion and at the end of it I felt like charging her for a therapy session. "I cannot keep writing blogs that work in the phrase 'DUI attorneys' 20 times in 2 paragraphs!" she wailed. I looked at the blog and it was dreadful. She asked me if I would write blogs and I said sure, and quoted her double my normal price. She never called me back.
I didn't lose any sleep over it.
See the above sentence, "I didn't lose any sleep over it"? That brings me to my next point.
Writing a blog is not like writing for your high school English teacher. You don't have to write perfectly composed paragraphs with a topic sentence and supporting sentences. On the web, a paragraph containing one sentence is OK.
Bullet points are good.
White space on the page is good.
People tend to skim articles on the web, not read them in depth. They pay attention to bullet points and lists. Long, dense paragraphs are not the best for your typical article on the web.
Here is an example of an interesting article, from Reuters: Crisis forces Greeks to skimp on weddings, funerals. Notice all the one sentence paragraphs?
[FYI: Reuters is a respected source of news and information. Years ago when my brother was in the Army, he consulted Reuters for information he then used in briefings for generals. He's a tough critic of news outlets.]
Length is also important. Most people don't read long articles on the web. They want the information short and succinct.
Titles are also critical. I find that the blogs that attract the most hits over on my personal blog The Crab Chronicles are the ones that have titles like The World's Best Pound Cakes. If people want to make a great pound cake, that's the type of phrase they put into Google or Bing.
So your English teacher might hate what you write for the web, but don't worry about it. It's a whole new world out there and great SEO is the best letter grade you can get!