The difference between the simple present and the present progressive is that the simple present does not consider limited duration of the activity, while the progressive both considers duration and implies limits to it at either end of the activity. My sister goes to high school -- This simply states the situation: she is a high school student My sister is going to high school -- This supplies the same basic information (she is a HS student), but also limits the time to 'currently': perhaps she just started, or perhaps she will soon finish, or perhaps she is just travelling to the place at the moment. In some way, her attendance is limited.
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