Since there are 4 students in total ,
There are 4 choices for who is going to sit in the front. The remaining 3 students can sit at the back in 6 ways( 3choices for the extreme left student followed by 2 choices for the student sitting in the middle followed by one choice for the student sitting at the extreme right).
Therefore, the total number of ways will be 4 time 6 or 24ways