With the exception of top of the line tournament style paintball marker, most paintball guns are semi-automatic.  This means one ball comes out per trigger pull.  It also means your gun will shoot as fast as you can pull the trigger!  In case semi-automatic isn't fast enough for you, more trigger options are available as an upgrade for most paintball guns; these are called electronic triggers.  Most e-triggers offer at least 3 firing options, semi-automatic, 3 round burst and fully automatic.

As you get more addicted to paintball, sometimes it becomes tough trying fit it all in.  Keeping your grades up while playing paintball is a hard thing to do.  Especially if you're playing other sports (along with paintball), you need to find time to get your school work done and still be able to play.  You'll have to manage your time wisely while playing paintball during the school year.