Here is a company that will help:
You could also search on this website:
I would suggest that you have your classmates help you. You could post it on facebook and have the word spread. I hope this answers your question. If not, then please reply.
Greatreunions has the online assisted feature of find last known addresses. You might want to try this link:
I would also contact the school to see if they have a list with addresses, phone numbers, or parents. You could probably contact the parents to get the info. I do not know of a database service. You could just search online.