Concatenate to make a label

Hi all, some help please?

I have some cells on a worksheet named, as an example, grade1, grade2, grade3, etc. I also have a cell, M16, which contains a number which is the grade number. What I want to do (this doesn't work) is place in another cell a formula thus.....

= grade & M16

so that the cell will display the value from grade1 if M16 is 1, from grade2 if it's 2, etc.

If I change the formula to be

= "grade" & M16

then the cell displays "grade1" (or grade2 or whatever), but just as a string, not using it as a label. How do I concatentate the word 'grade' with the contents of a cell and use the result as a label ?

Richard