I wouldn't consider recognizing a school district alumni for a significant accomplishment an out-of-the-ordinary occurrence. Scroll through Twitter enough and you see this all the time. To take things a step further, consider sending a hand-written postcard to the parent's home of the alumni. Not only will the person getting the postcard appreciate it, there is a good chance the parents will be impressed as well. I have used Vistaprint to help me create my school district-specific postcards and have been very impressed with the quality of prints I get for the price.
Postcards to Alumni