Mika Wenedlius already mentioned about relational database. So, in addition to His answer:
CREATE TABLE [dbo].[Students] (
[StudentID] INT IDENTITY (1, 1) NOT NULL,
[StudentNumber] NVARCHAR (50) NOT NULL,
[EnrolmentDate] DATE NULL,
[Class]
Well...
Class
is not a part of student (attribute).
Class
is an object which describes a collection of students (but knows nothing about students!):
YearID -- refers to year's table (^__b style="color:orange">YearID - PK, ^__b style="color:orange">StartY [start of school year], EndY [end of school year])
... and so on..
Finally, you have to create a third table, which should store all students in a class -
Class_Student
table:
-- refers to class's table
^__b style="color:blue">StudentID -- refers to student's table
This is how
many-to-many
relationship should be defined in your case. As a picture is worth thousands of words....
----------- ----------------- ---------
| Student | 1---∞ | Student_Class | ∞---1 | Class |
----------- ----------------- ---------