First you need to go talk with an IT administrator at your school to find out where student account information is stored. Most likely it will be stored in LDAP or a database. Then you need to ask that person to grant you the necessary permissions to access the account information. And you also need to know all of the information necessary to accces that information, such as database connection URLs, LDAP server name and port, queries to access the info, etc.
After you have done that, then you will ready to look at what can be done within JBoss AS to access that account info. For example, if the student account information is stored in LDAP then you will need to define an LDAP login module within server/xxx/conf/login-config.xml. If the info is stored in a database you will need to set up a database login module in the same file.