~로/으로 is for physical directions/movements while ~에 is about the usual, self explanatory business. 나는 학교로 갔다 = I went to the school (you went to the parents meeting that happened to take place at school for example) 나는 학교에 갔다: I went to school (you are a most probably a student or a teacher)

a place + -(으)로 : to the direction of a place (emphasizing the direction or path.) a place + -에 : at the point of a place (emphasizing the destination.) -(으)로 is used with a verb of meaning of coming or going. e.g. 그는 학교로 갔어요.(O) He went to the direction of the school. 그는 학교에 갔어요.(O) He went into the place of the school. 그는 서쪽으로 갔어요.(O) He went to the west. 그는 서쪽에 갔어요.(X) 그는 위층으로 갔어요.(O) He went upstairs 그는 위층에 갔어요.(O) 그는 위층으로 살았어요.(X) 그는 위층에 살았어요.(O) He lived at upstairs.