I want to cancel my subscription when the trail period finish but i couldn't find the way without having to contact my school account admin. This is very strange as I didn't need him at all when i registered. There must be a way but i still couldn't find it. Thank you in advance for your advise.
Your account and subscription is managed via your school and that means that you need to contact your school's admin for Adobe products to change whatever change you want to apply. It shouldn't be possible to take a subscription (option) that is not included in what you school offers. If, however, you are using a different account than that one associated with your schools account then you need to use that account to cancel the trial.
I would recommend to contact Adobe customer service on that to get more information: Adobe customer care can be contacted here: https://helpx.adobe.com/contact.html - click the small callout at the lower right of the screen and type "agent".
Regards, Abambo Hard- and Software Engineer and Photographer.