AS-Level retake email help!

Hey I got into year 13 but I want to redo my AS Levels, just wondering if anyone could help me with starting off an email to my head of year about saying I'd rather not progress into year 13, I'd like resit last year. Thanks

Some sixth forms will not allow this, I know mine does not anymore.

Firstly, check it is possible and explain your reasons why. Then progress onto the finer details later.

I already know this is possible, many people I know have already requested to resit the year.

Cracking!

Just say...

a) what went wrong and why
b) how you're going to improve
c) what you want to achieve (don't be too overambitious - you can just say "go to a good uni to study..."