I'm sorry that you are experiencing this tough situation.
I will give some examples of things that you can try saying, but it is important to remember these things:
we can't change other people (I have tried a few times!)
we can't "make" someone feel a certain way (younger children are much more vulnerable, so they are an exception to this... And violent crimes)
Your mother's reactions to external events/words/actions remain solely in her brain and were learned from past experiences.
Your reactions to external events/words/actions remain solely in your brain and were learned from past experiences.
Both of your reactions to each other's behavior is valid. (valid is not necessarily healthy or constructive)
Knowing this, we must be careful to not point fingers when working through problems.
Let's look at an example conversation:
You: Mum, you're treating me unfairly and it's stressing me out. Don't you care about me?
Mother: I don't know how you could feel that way. I only want what's best for you.
Notice, both of these statements seem reasonable, and both could be argued to infinity. The problem is, they are both conflicting statements and cannot possibly both be true. If your mother wants what's best for you, she won't treat you unfairly. If she doesn't care about you, then she can't possibly want what's best for you.
Let's simplify what is being said to the most basic level.
You: You're being a bully and it's hurting me.
Mother: I'm not being a bully; I'm a nice person
In this example: After two sentences, notice how both of you are already locked in disagreement. Lose-lose
Briefly from another angle:
You accused your mother of something.
Your mother ignored the accusation and even gave herself a moral pat on the back.
Notice how this conversation is skewed in favor of your mother. If you accuse her of something, the outcome of the conversation is completely dependent on whether she accepts or rejects the accusation. In other words, she holds all the power in this exchange.
How can we try to avoid this accusative and stressful rabbit hole of a "conversation"? Let's level the playing field.
You: Mum, I'm not sure why, but after I get an answer wrong, and after you correct me, I feel upset. I don't think it's your fault. Its really important to me because I think my being upset is affecting my classwork and motivation.
...and wait. What will she say?
This will remove all requirements of your mother accepting an accusation. This shifts the power from your mother to a much more neutral position. If both of you can practice doing this and be truly curious about each other in the process, it will lead you to learn a lot more about each other's preferences, past experiences, and fears. win-win
Unfortunately, based on my personal experience, the likelihood of your mother adapting this equal, negotiation-based communication strategy is slim.
I recommend giving this book a read if any of this makes sense to you. It will have many more examples and branch into other family situations. And it will help you build a good foundation.
Source: Real Time Relationships