AFAIK, the datasource binding is 1:1 - a pool of connections all have the same source connection characteristics.
The number of datasources in JBoss probably won't be an issue - but the threading in the JVM may drain resources. It may also be an issue for your Oracle DBMS with that many connections - you'll just need to tweak the connection and memory settings on both JBoss and Oracle.
You probably don't need to have each student have their own database name and password unless they need to log into Oracle as well.
I'm not sure if you are after more information than that.