Yes, you can drop classes after the quarter starts. Starting the 11th day of the quarter you will need to get instructor permission to drop a class, the class will show as a "W" on your transcript for withdrawal, and you be charged a $15 add/drop fee. No "W" will be given after the first day of the seventh week. Instead, the student will need to contact the instructor about withdrawal options.
Through the first week of the quarter you get an 100% refund for the tuition that was paid if you drop a class. If you drop a class the second week and third weeks of the quarter you get a 50% refund*. No refunds are granted after the third week of the quarter.
*Summer quarter deadlines differ, please refer to the Summer class schedule for details.