Chodzić represents habitual going somewhere so we usually translate it with simple tenses. Iść on the other hand indicates that someone is walking at this exact moment. So continuous tenses.
It is a very common distinction with 'moving verbs'. We have chodzić-iść (to walk), pływać-płynąć (to swim), biegać-biegnąć (to run) etc.
Keep in mind that the imperative of iść and chodzić works a bit different. Here some examples: Come here. - Chodź tu. Let's go. - Chodźmy. Go to a concert. - Idź na koncert. Come to a concert (with me). - Chodź na koncert (ze mną). Go away. - Idź stąd. Chodzić usually means (in imperative) going somewhere here (hither) and iść usually means going somewhere elsewhere (thither).
"I am going to school" has two meanings, one that i am currrently on my way there (idę), but the other means that i am enrolled in school, or i am a student. You can't really make a habit of a continuous state, but does iść or chodzić reflect this second meaning, or is there a better way to say it?
Chodzić reflects this second meaning. It could also mean that someone is often walking to a school. Though iść can mean only the second thing. Oh, and one second meaning - idę do szkoły can mean I am getting enrolled in a school, I am starting the education in a school. Just as idę na uniwersytet (I am going to an university) rather mean I am becoming a student at a university than I am walking to an university, though the second meaning is also fully legit, just less probable.
ChristineB958863 don't worry about it, it will come natural to you in time. Polish verbs of motion are very tricky for learners to become accustomed to but with practice, you will become more used to them. I can recommend an article that might help and goes into some detail https://www.clozemaster.com/blog/polish-verbs-of-motion/