It is good that you are selling now. The problem, if there is one, will not affect you. Other actions you could take could enhance your home's value now.
However, it is my understanding that the site selection is the problem in Kensington, pretty much eliminating Rock Creek Hills if the new middle school is build there. Although the Board of Education approved the site, it is facing stiff opposition ...
With a targeted opening in 2017 it is too soon to tell in my opinion what impact it will have and it might not effect your current selling plans at all at this point unless you are across the street or neighboring the proposed site. A Realtor familiar with the area and the plans would certainly make his/her buyer aware of it.
One can look at the glass half full or half empty - if plans move forward and the school is under construction, a savvy Realtor would choose to highlight the benefits in all marketing.
This would likely be a concern for a buyer. However, Kensington is a great area with very good buyer demand. If your home is priced right for the current market, you should do just fine. I doubt that buyers would discount your home's value significantly.
Hope that helps. You can see basic stats for Kensington inventory at this link: