"학생들이 학교로 걸어요."
Translation:Students walk to the school.
(N)에 걷다 - walk to (N) [N, destination]
(N) 안으로 걷다 - walk into /enter (by foot) [N is a location; 안으로 depicts a transfer to that location]
(N) 안을 걷다 - walk inside [N is a location inside which the action takes place]
(N)까지 걷다 - walk up to [N is the end limit of the walk]
(N)로 걷다 - walk toward/towards/ in the direction of N. [N, not necessarily the destination]
Agreed. In English, these 2 tenses tend to be used interchangeably. But there is a small difference and it really depends on what the Speaker wishes to convey: to describe a habitual action, present simple; or to describe an action that is occurring at the moment the statement is made, present continuous.
When the action is "not habitual", then the present continuous (both in English & Korean) has to be used.