Three tables: tblStudents, tblCourses, and tblStudentCourse.
Example:
tblStudents
ID Name Etc...
1 S1
2 S2
...
n Sn
tblCourses
ID Name Etc...
1 C1
2 C2
...
m Cm
When Student Sx takes a course Cy, add an entry in tblStudentCourse:
ID SID CID Etc....
z Sx Cy
As I see it, it is one to many relation