I agree with everything written above. I especially echo the part about telling your parents how you feel.
In addition, I want to add that dealing with stress & our reactions to it is something that we ALL have to manage in our lives, no matter how old we get! I still have to work on not being impatient or getting frustrated with other people too. So cut yourself some slack on this.
When I find myself in those types of situations, I try to ask myself the following questions before I react:
(1) Is this something that will really matter to me tomorrow? In a week? Or more?
and
(2) If I say or do something, is it likely to get me what I want from these people?
If the answer is not a "yes" to both, then I try to let it go. I may be annoyed then, but within a few minutes or an hour, I feel a lot better than if I had snapped.
[Another option is avoiding situations that you find frustrating, but since you're in school, I'm guessing you have no choice.]