how to use rfid for student attendance system

Question

Hi friends,

 

          I would like to use RFID for student tracking system. but i am not very well in RFID. please tell me how it is work for attendance. whether we need two different RFID reader for Intime and Outtime process or we can use single RFID reader for both Intime and outTime and how can we differentiate the particular entering time is Intime or Outtime. please provide any documentation or article related to this application.

                   Thank you