I think Jasper makes a lot of good points and you should carefully read his suggestions and consider them. I think your essay comes off as a bit defensive. In my opinion, you'd be better off taking the subject of roleplaying games more "matter of factly" rather than assuming your reader has a negative view of them.
My other opinion on the issue is just that, an opinion, and you should feel free to ignore it. I think you focus too much on the benefit of D&D for teaching mythology and not enough on the emphasis on (1) Language Skills (which I consider to be probably the primary benefit I've derived from such games) and (2) Math (which I consider the secondary benefit of such games). I think that Mythology comes well down the list of benefits, both in terms of how much the players actually benefit from it (most campaigns are not set in ancient Greece for example and don't use real world cosmologies and pantheons) and how much benefit the average "layperson" will percieve from it.
I think the ways in which D&D benefit language skills are manifold. First off, I think the Fantasy gaming genre encourages players to read a lot of fiction and the simple act of independant reading is something that many teachers are hard pressed to get their students to do these days. I also know that I've read dozens of non-fiction books because they dealt with issues of sociology, technology, geography, cosmology and ecology that were relevant to my world-building skills as a GM.
Even if players don't read additional fiction or non-fiction, they will still be reading the rulebooks and the PHB alone has a page count considerably longer than many novels and textbooks. Also consider that it is full of RULES. Each of these must be considered and interpreted and that heightens one's critical thinking skills.
The other thing that D&D rulebooks are full of is vocabulary. The default world of D&D deals with a finite set of topics ("Swords and Sorcery" is probably the most succinct way of saying it) but folks hate redundancy of terminology in their gaming books. So the authors of these books hunt down every synonym in the world for the various ideas presented. Your average high school student does not know the word "Thaumaturge". The average D&D player does.
As far as mathematics goes, right up front you have Point Buy as an illustration of "The Law of Diminishing Returns". Also, I agree with bolen above that dice probability is a good illustration of what "The Math of D&D" can teach kids. Ask the average high school student what the average result of 3d6 is and they probably won't say 10.5. D&D players also begin to understand that a single roll where there are equal probabilities of any result (like 1d20) produce a flat distribution of results (assuming a fair die). But rolls like 4d6 or 3d8 or any roll of XdY where X is not equal to 1, will produce a bell curve. This information may not seem hugely relevant to life at first glance, but it is.
Consider this: You are going to buy some stock. You could decide to buy a single stock and put all your money in it. Most brokers consider this a risky investment. This is analagous to rolling your d20 (though hopefully you've done some research and weighted the odds in your favor a bit) in that you will either do well or you will do poorly. Either way, all your eggs are in that basket. But if you diversify into several stocks, it is like rolling your Fireball damage. Some may go down (rolling a 1) and some may go up (rolling a 6) but they'll probably average out to a modest return. They might all tank (rolling all 1's and 2's on your Fireball damage) or they might all skyrocket (rolling all 5's and 6's on your Fireball damage) but odd are against it. And the odds are more and more against it the more you diversify, just like the odds of rolling all 1's or 6's goes down as you roll more and more dice for your Fireball damage.
Now of course there are other ways to impart this same lesson that have nothing to do with D&D. But you'd be hard pressed to get the average 10-12 year old to understand them. Gaming is a way to introduce these concepts at an early age that lays a foundation for their later understanding of how they apply to life.
Lastly, I think that D&D is a good forum for the consideration of ethics as the players mature. While the "Paladin Debates" here on the boards never seem to actually have a resolution, I think that a lot of the points raised are good food for thought. The Law vs. Good dichotomy inherent in every Paladin sets up a perfect argument for the "Good of Society vs. Wellbeing of the Innocent" situation that crops up in our modern lives.
I hope that some of this will be of help to you. I applaud your goal of getting teachers to understand the benefits that roleplaying might have for kids. And I will say that I'm slightly less pessimistic about your odds for success. I have several friends who took "D&D" as an elective in 6th grade (and this was back in the early 80's
) and I took "D&D Classes" at the Jr. High School during the summer back then too.
