With no restrictions, we can figure out the answer to be 13! by the following analysis:
For the first position in line, there are 13 different students who could fill that spot. If we fill it and proceed to the next position in line, there are now only 12 students left who can fill it, since one is already in line. Then the next position only has 11 possibilities, and the next 10, and so on.
Multiplying all of this together gives us 13*12*11*10*9*8*7*6*5*4*3*2*1 or 13!
