Chodzić and Iść are actually the same aspect, imperfective. In Polish, the imperfective is used to express both habitual action, and continuous action. So usually you would use the same verb to say both things, but these two verbs seem to be a bit of an exception.
For the first time I saw a black box above the lesson telling me that my translation "I walk to school" was wrong and explaining the difference between Idziemy and Chodzimy. That's amazing, I'm very impressed with how useful that sort of thing will be. Usually I have to go to the forums to find out things like that!
I think this difference iść chodzić applies in the context of school. Idę do szkoły ( I am going) and Chodzę ( I go regularly ) szkoły. But usually you would always say Ide do domu ( i go home and I am going home ) but I never saw Chodzę do domu ( I go everyday..). .. Experts please help :-) Thanks!