Exposing students to Linux will have a long term impact on it's growth in other areas. The primary reason many companies have spent millions of dollars on Microsoft software is that people know it. In 5 years today's 9th grade students will be in the workforce. If they're already comfortable with open source software, it will make it that much easier for open source software to move father into other sectors.
Unfortunately at the moment we're in a situation where propriety software has become the default standard everywhere. People are unwilling to learn how to use alternative products because it's not what they'll need to know in business. Businesses are unwilling to change to alternative products because they'll have to face retraining costs. What this means to schools is that there's a greater emphasis on teaching how to use certain products to students rather than teaching them the basic concepts behind the use of those products.
Instead of teaching students the basics of good layout for essays, teachers often end up teaching students how to layout their essays using a particular product. Instead of teaching students basic computer presentation skills teachers often end up teaching students how to use a particular product for presentation. These lessons are useful but they did not achieve their original purpose. Exclusive use of an open source software product won't solve this problem either. However, access to a wide variety of open source software products allows teachers greater choice of packages to best illustrate their lessons and students greater exposure to how other packages may perform tasks.