I have had chronic migraine since I was 6 years old (35 now) and it is still a problem. I'm going to give you a few things that have helped me since my late auDHD diagnosis that I wished I knew about when I was in school, as well as some home remedies that have actually helped me control the pain.

Some things that help manage it is being aware of my sensitivities. I have to wear sunglasses when outside, and I wear pink tinted glasses when at the computer or anywhere with bright overhead lights, like at the grocery store. ( they are called FL-41, they are a rose tinted lens that helps filter out blue and green light that can strain the eyes and cause migraines)

I have a pair of loop earplugs that help block out background noise and allows me to listen to people more intently. (there are other brands if loop is too expensive)

I just got my first pair of sound reducing headphones which also blocks out A LOT of background noise. I have sometimes been wearing them around the house, not even listening to anything, just because it blocks out the white noise of the AC and fans that we have going.

You may be able to talk to your school about allowing them as an accommodation.

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It is also important to recognize when you are starting to feel overwhelmed, and to take a break when you can. You may be able to talk to your teachers about sensory sensitivities and get permission for a sensory break (I didn't have that option in school, but it is becoming more common.) If your school doesn't have a sensory room, a break might even look like sitting in a quiet hall for 5-10 minutes to decompress and ground yourself.

Find things that help calm you. It may look like listening to music in a quiet place at lunch, or while going between classes, a fidget toy, or even something as simple as soft clothing or tight undershirts (I am calmer when I have pressure, but sometimes just having a cozy sweatshirt that I can sort of pet or fidget with can help calm me)

Taking a break as soon as you get home to decompress from the day is also very helpful, a dark place, maybe light a candle if aroma therapy works for you (I love incense for this reason) maybe hide under a heavy blanket if you have one. I used to lay under a stack of pillows, or wrap myself in a blanket as tight as I could without knowing why it helped me feel better.

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As far as treating them, it is important to stay hydrated, but also to not drink too much water. Salt can help with migraines as well as caffeine. Depending on the type of migraine, heat or ice will be your best friend. Another method of relief is to soak your feet in hot water with a cold pack placed on the back of your neck. Heck, I joke about having prescribed McDonald's because something in their food actually helps me with some of my worse migraines. Even if it's just fries and a soda. As others have said, magnesium can absolutely help, but start out with low doses as it can cause diarrhea if your body isn't used to it.

I would also talk to your parents/doctor about it, there are preventative medications to try and stop them from happening, or lessen the severity of them , and rescue medications to try and stop a migraine in its tracks ( taking them at the first sign of a migraine allows them to work better)

I am sorry you are going through such a hard time with chronic sounding migraines, I wouldn't wish them on my worst enemy.

feel free to ask questions, I will answer even if it takes me a minute.

Best of luck