First, and most importantly, unlike apps for private use, schools pay per device for your application. This is new for the 2011-2012 school year, so schools are feeling a lot of sticker shock. This is going to drastically affect your price point.
Second, schools have to pre-pay for their volume purchase, in vouchers starting at $100. Expect school systems to set a budget for apps at the beginning of the year, use one PO to buy the vouchers, and then not buy more except in very extenuating circumstances. (Your app will not be an outstanding circumstance. One by Apple or Pearson might be.) School budgets are very involiatle and only refresh once a year; if a school cannot afford your app in October, they cannot afford to buy it until the next September.
Third, schools do not have a way to handle in-app purchases (yet?).
Finally, you can choose to offer schools a 50% discount on purchases of 20+ copies of your app(and only a 50% discount, no more, no less).
Expect this to have a strongly downward price pressure on your app. One school I know only looks for free apps, and finds Apple's Volume Plan too cumbersome to use. My wife's school, K-8 has an app budget of somewhere just south of $1000. Their policy was: each grade level must choose, as a team, one application that costs $1.99 per unit or less. Plus free apps. That's it for the year.
In short, if you're looking to hit the classroom, you're probably going to need to stand out in both polish and price. Polish to get noticed above the others, price to get in under budget.
Links to check out:
Apple's FAQ: http://www.apple.com/education/volume-purchase-program/faq.html
Blog post on what it looks like from the educator's point of view: http://learninginhand.com/blog/app-store-volume-purchase-program-explained.html