One thing I've been diving a lot into this past week is learning about learning, which has been super interesting. Most of what I've learned has been through Dr. Justin Sung, who's a learning coach and makes a bunch of great youtube videos. (Almost all of this is summarizing what I learned from this video)

If you're like me, if you take notes, it's probably the standard handwritten/typed full page of words, directly copying down words of powerpoints or what the teacher says. Maybe the odd diagram or two, but mostly just writing down things slightly worded differently or verbatim, in a linear fashion down the page in bullets or paragraphs. This is seen as "normal" notetaking, but it's actually one of the worst ways to write notes, and is only slightly worth doing.

Our brains don't hold information in a linear way like that, and neither does the brain of the person teaching the info, whether that's a professor or a textbook author. Our brains hold information in a complex network, made up of countless relationships. When we learn new information, our brain then tries to relate that info to other info it already holds. And when it can't, it's much more likely to forget it. (Part of why languages are hard) Our brain uses 20% of your body's total energy, so it's very good about preserving that energy, by getting rid of unnecessary information. That's great in some ways. It'd drive us insane if we remembered every minute sensory detail of every second. But our brains often throw away info that we actually want to learn. When we forget things we study, it's because our brain deems it unimportant and irrelevant. 

So then our task as learners is to make our brain recognize that info as relevant. When we just copy down linear notes, or speed through a book without taking ample time to process the info, then our brain forgets most of it very quickly. (About 90% of new info after one week) The primary way of fixing this is through improving our encoding methods, which is how we transfer new info to our memory and make it stick. (Most "genius" students who can ace their exams with little to no studying are often just really good at some of these encoding methods, even if it's unconscious) For example, instead of linear maps, try mind maps, where you draw out info in a super summarized, visual format where you spatially arrange concepts and show relationships and make comparisons. (Plenty of examples and youtube videos on how to do them)

The very act of drawing the mind map makes your brain compare ideas to see how they relate to each other and to info you already know, which in turn makes you remember more of it. The key is to spend an equal time digesting info as consuming it. How often do you read a chapter of a biology textbook, then just sit and think about the content? Not writing it down, not highlighting, just thinking and processing it in your brain to relate it to other concepts and understand it. It can be time consuming yes. But if you're only retaining 10% of info, then you're already wasting time, and spending more time digesting will ultimately result in more efficient and higher quality learning.

Summarizing is also key. It helps you to remember the actually important bits, and that act of deciding what info to prioritize also helps your brain remember it better. One strategy that helps is delayed notetaking. After learning a new bit of info, especially via lecture, try to wait 30+ seconds before writing it down. Your brain can't juggle all that info for very long without having to write it down, so it forces you to summarize that new info to be able to remember it.

This all isn't to say that route memorization doesn't have its place. There's plenty of types of learning that doesn't really have much relationship to other info, like memorizing formulas or language vocab. In those cases, applying the info through practice problems/sentences is key, though you'll likely have to just grind through some of it with flashcards and the like. Also in high school, more of the learning tends to be lower level and not require as much higher order thinking (look up Bloom's learning taxonomy for more info on that), and there's a lot of brute memorization. But in some of the science classes like chemistry and biology, or history, can be learned really well via mind mapping and other techniques. It's also useful to pre-study before classes, since you already have a vague outline of the big picture and can fill in as the teacher gives the lecture

TLDR: When learning, if you spend ample time mentally organizing new info and focusing on how it relates to other info, how it compares and contrasts with each other, then it makes your brain consider it more important, and therefore remember and understand it better. 

I'd highly recommend the video linked above, despite it's length. It's really a goldmine, and most of ya'll likely spend 5 hours a week on the shard or scrolling anyway