How many pages of notebooks should be prepared in high school? I don't want to change every semester.

It depends on what you want to record in this book.

If you take notes in class, no matter how thick the notebook is, it is not enough.

I suggest you buy a hardcover notebook, 100 pages or so. It only records the special properties and reaction laws of substances.

For example, what are the characteristics of alkali metals, sodium and potassium? . . Comparison of reducibility and oxidation of alkali metals, etc.

That record can be divided into several parts.

Such as metallic elements, nonmetallic elements and organic substances, or depending on the type of reaction.

It depends on how you fit in.