how long do you go to secondary school for

Completing the CAPTCHA proves you are a human and gives you temporary access to the web property.
If you are on a personal connection, like at home, you can run an anti-virus scan on your device to make sure it is not infected with malware.

If you turn 16 during the school year (between 1 September and 1 July) you can leave school after 30 June.
If you turn 16 between 1 March and 30 September you can leave school after 31 May of that year.

What happens next
There is no need for you to accept the place offered to your child at any Hampshire school. However, please let us know in writing if you no longer need the place so that it can be offered to another child.

If you were sent a letter with a Unique Identification Number (UID) in September, please note that you will only be prompted for this if the details you enter for your child do not match those held on our records. Please continue with the application even if you are not asked for the UID number.
Once you have made your application you will need to submit a scan or photo of a utility bill (gas or electricity) dated within the last three months, showing usage at your address.

References:

http://www.gov.uk/know-when-you-can-leave-school
http://www.hants.gov.uk/educationandlearning/admissions/applicationprocess/year7
http://www.buckscc.gov.uk/apply-for-a-school-place/apply-for-a-secondary-school-place/
http://www.gov.uk/check-a-university-is-officially-recognised