In my school, our ranking for each subject is displayed in our school reports under each respective subject. I'm not sure if there's really any other way to determine your ranking if your school refuses to tell you.
Our school gives our ranks under the subject, but in your case you can find out your rank by maybe asking you classmates their marks add there marks on excel and you can easily find your rank
WARNING: Some of your classmates may find it rude that you are asking their marks.
Try asking your parents to ask your ranks tell your parents to tell them that they are interested in your ranks maybe your school wont refuse it to them because they are interested in their child's rank.