Yes, you may drop out at anytime, however; if you plan on withdrawing out and have taken out student loans/grants there is a predetermined time frame in which the school has to return any payments received. (Ask your school counselor to find out how many weeks you have if this is something you are interested in.)
If the school is required to return funds then you will only be responsible for the difference of what was spent. If you do not drop out soon enough then you will still have to pay your student loans back in full (in installemts unless you can afford to pay in full).
If you have paid out of pocket for you tuition then the same applies they will refund you any overage you have paid if you withdraw within their specified time period. Otherwise your payment will not be reimbursed.