You'd be surprised how many of your old teachers are still alive and kicking. Many of mine were not much older than me 6-10 years older, and to me they were old women, but really they were in their 20's!
So look them up, and you can expect a really friendly response, at least the three I thanked, two remembered me, one didn't but they were all happy to know that they'd had a positive effect on SOMEONE.