You are not required to begin repayment of Federal Direct Loans until six months after you a) graduate, b) totally withdraw from classes during a term or c) drop below half-time enrollment.
As long as you maintain half-time enrollment and attendance each term, you are not required to immediately begin repayment of your loans. This is called In-School Deferment.
The six month period between when you “leave school” and are officially required to begin repayment of your loans is called your Grace Period.
Half-time enrollment is defined by the U.S. Department of Education as attendance in 6 to 8 credit hours that are eligible for financial aid.
Should you totally withdraw from classes before the end of a term or stop attending at least 6 eligible credit hours within a term, you enter your grace period effective the day that you dropped.