To get into a good university (such as MIT, Yale etc)
Do you need to be in all honor classes to be accepted? And also do those colleges will most likely not accept you if you’re not?
Generally, unless your school doesn’t offer honors, yes. AP’s (when available) are also expected.
Honors & regular teaches primarily the same thing. Based on the teacher, you might have more work in one class over the other. When you have to chose on, chose Honors. Plus, honors boost up you wieghted GPA by 0.04.
All honors? No. Mainly advanced courses and showing them that you’re challenging yourself? Yes.