Finding out information about a person who goes to your school can be accomplished in a few ways depending on the school you're attending. Living in the digital age, there is a better-than-average chance that the person you're looking for has some kind of presence online. You can also attempt to find that person the old-fashioned way --- by asking around and speaking to other people with whom you go to school. These can be great ways to find out a little information --- such as likes and dislikes or general interests --- about a classmate.
Use Facebook (see Resources). When a user sets up a Facebook profile, he has the option to input the current school or university he is attending. Type the name of your school into the "Search" box on the Facebook site to view a list of people who have specified that exact piece of information on their profiles. You can then browse through the list of results until you find the person who goes to your school, if that person has a Facebook account.
Use the Classmates website (see Resources). Classmates is a service that allows users to set up profiles and either reconnect with people they used to go to school with or connect with new people they currently go to school with. Create an account on Classmates in order to search for classmates by year.
Talk to your friends and teachers/professors. If your friends don't know a person, friends of friends might. Likewise, teachers and professors can interact with hundreds of students on a daily basis, so it's likely that someone knows the person you're looking for and can help you find out more information about her. Teachers and professors likely won't reveal any personal information about an individual, but they can give you a little more basic information about a person.