http://www.backtoschoolstore.org/ is now a full-functioning site, so someone must have bought the .org from the person who had it parked at Sedo.
Your best shot is to approach BackToSchoolStore.org and see if you can get at least $1,000. Sometimes it is best to test them out to see how interested they may be, and other times it is best to mention a price. You would think they would be smart enought to pay thousands of dollars for the dotcom, but I know from experience that some people would rather not have someone else profit from a similar name.
I would check out their site and try to figure out just how big their business is, and if it seems substantial I would go about it with a serious approach. Maybe call them or email multiple parties and let them know the value. It is an art, not a science. The key is to make sure they know that the name is worth more to them than the price you are asking, and you also want them to know that you aren't getting a windfall at their expense (even though it is a generic phrase/term).
I sometimes use an approach like this:
Greetings,
I acquired the domain name BackToSchoolStore.com at a domain auction a few years ago. I have decided not to develop it, and therefore it is available today for $3,500. Please let me know your interest so that we may conduct a quick and easy transaction.
Now, remember, there are 100's of different variations of the above. Sometimes it is better to list the price, and other times not. Sometimes it is better to let them know why the name is valuable to them, but in this case it is quite obvious (they have the .org), so you don't really need to explain it to them. Get as much information about them as possible and then develop your gameplan.
Also, in this case, even though they should already have an idea as to why it would be valuable, it might be just as well that you let them know that the name gets good traffic.....targeted traffic, and there is a likelihood that a significant percentage of that includes people looking for their site. You can only do this if you are not infringing on their trademark. Since this is a generic term, I feel that they won't feel entitled to the name as much as some others might, and it isn't likely they would spend the time and money on a UDRP against you (that they would probably lose, anyways). If they think they are losing sales and they feel you are not taking advantage of them, then your job gets much easier.
There are many ways to skin the cat, and part of the fun is figuring out an approach that will maximize your return without blowing the sale, so use your own creativity and common sense. Put yourself in their shoes. What approach would you respond best to?