It might be helpful to tell them that you reached out for help and share with them the information I am giving you. If you believe that your parents may not be supportive, then you must talk to a school counselor, or other adult. You do not mention feeling suicidal at this point, but if you feel that you want to harm yourself or others, contact a suicide hotline, emergency room or the police immediately. I have a few questions for you. You talk about school creating a lot of pressure.
Many young students are under a lot of academic pressure and are pushed to perform.
This is either pressure coming from the outside like your family or the school or from your own pressure on yourself. It is important that you look at all you are doing, school, sports, family obligations, church, everything and see what can be done to reduce some of the pressure. Pre adolescence and adolescence is a time of self discovery it is important to feel accepted and valued and have the proper balance of support and independence. Your parents and school counselors need to be involved in helping you make some changes in this area. Some of what you are describing, the feeling like you could cry, yelling at people for no reason, can be caused by changing hormones.