가면..., 갔을 때... 갈 때마다...
집에 가면 = when I go to school
집에 갔을 때 = when I went to school
집에 갈 때마다 = whenever I go to school

1) I know 갈 때 and 올 때 are incorrect, but why?

2) Are 갈 때마다 and 올 때마다 both correct?I read that 갈 때 and 올 때 are wrong, but I just saw some sentence examples using them. HmmWow, obviously not "school", but "home"!

Question

가면..., 갔을 때... 갈 때마다...
집에 가면 = when I go to school
집에 갔을 때 = when I went to school
집에 갈 때마다 = whenever I go to school

1) I know 갈 때 and 올 때 are incorrect, but why?

2) Are 갈 때마다 and 올 때마다 both correct?I read that 갈 때 and 올 때 are wrong, but I just saw some sentence examples using them. HmmWow, obviously not "school", but "home"!

Answer

oh, you can use 갈 때 as well
when i go home => 집에 갈 때

"집에 올 때" means "when i come home"

"집에 올 때마다" means "whenever i come home"