That's not even a grammatical rule in English, merely a convention handed down from lazy American printers who wished to avoid misaligning columns - the well-rounded reader will note that that exact opposite rule is in place in Britain, the very wellspring of the Queen's English. Do try to learn something about your own language before you presume to lecture others about it.
Also, one should not begin a sentence with a conjunction such as "but," as in, "But this is not Vero Beach..."
A completely nonexistent "rule", perpetuated by generations of spinster-like fourth grade grammar pedants. Starting a sentence with a conjunction is both perfectly acceptable and perfectly grammatical. If you had ever read Shakespeare, Burke, the King James Bible, Johnson, or any other of dozens of classical English works, written by genuine men of letters - which, obviously, you haven't - you would have unavoidably noted that all of them contain dozens of examples of sentences beginning with conjunctions. Don't take my word for it, though - walk down to your local library, and check out a book or two. This may be an unfamiliar experience for you, but there are many friendly people staffing the library whose job is to assist the novice reader.
I'll forgive you for only having a "passing familiarity" with public schools, but generally they encourage students to speak their minds as opposed to telling them to "shut up and sit back down."
Of course they do - it's so much easier that teaching them, isn't it? Just let them spill their guts about how they feel - nothing is more important than self-esteem, right? Certainly not mere information, anyway. It would be cruel and unusual of us to encumber their opinionating with anything so mundane as a fact or two, wouldn't it?
I am not offended by those who share their opinions. When the ignorant and the uneducated spout off, blessedly unhindered by any connection to reality, however, it wastes my time, and everyone else's here. I am not obligated in any rational sense to reward the execrable, and if you, sir or madam, are responsible for the odious state of the minds that produced the posts that precede and follow yours, you should be ashamed of yourself.
As far as the illiterate and pedestrian manner that you claim this 15-year-old expresses himself with, you might think about what manner you are using when you compare a child's thoughts to excrement, and if that manner is really from "his better."
Consider, for a moment, whether you are really doing the child a favor by lying to him, telling him that his manner, style, and content are praiseworthy, when they are in fact, patently illiterate. Consider, for a moment, which of us does the child a greater service in the long run - you, who lies to him, or me, who tells him the brutal, but honest, truth. Which one of us will prod the boy to actually become a better writer, and thereby a better thinker?
You feed your charges a steady diet of spun sugar and Jolt cola, and then you have the nerve to be surprised and offended when someone points out that their teeth are rotting out of their heads. Wake up, I urge you - stop lying to them, and educate them properly. If you can.