It depends the way you say it. For you to say Gakou ni kimasu you'd have to describe the day you are in and still be in school in the same action. "I go to school" in that sense does not work, cause that is not the go of action but the go of description. The right word here would be "I attend school" or "I walk to school". Be careful english is not full proof. So in that case it would be Gakkou ni ikimashita (I went to school on that day but I'm not in that day anymore so the action is over).
The difference between both is very subtle and hard to grasp. I'd say the baest way to go about this would be to use the form "kara-made" so you'd give a time slot in which you go to school: gozen jyuuichijii kara gogo hachijii made gakou ni ikimasu. (I am in school from 11 in the morning to eight in the afternoon)
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It depends the way you say it. For you to say Gakou ni kimasu you'd have to describe the day you are in and still be in school in the same action.
"I go to school" in that sense does not work, cause that is not the go of action but the go of description. The right word here would be "I attend school" or "I walk to school". Be careful english is not full proof. So in that case it would be Gakkou ni ikimashita (I went to school on that day but I'm not in that day anymore so the action is over).
The difference between both is very subtle and hard to grasp. I'd say the baest way to go about this would be to use the form "kara-made" so you'd give a time slot in which you go to school: gozen jyuuichijii kara gogo hachijii made gakou ni ikimasu. (I am in school from 11 in the morning to eight in the afternoon)