"They enter the schools."
Translation:Mereka masuk ke sekolah-sekolah itu.
Why do you need the "ke"???
It's not really necessary to use 'ke' , although this sentence can have a slightly different meaning with/without 'ke' .
'ke' (particle) is normally used to indicate a location/movement, to indicate that you're going to a specific location.
'masuk' (verb) = 'to enter'
This verb also indicates a movement to a certain location.
That's why I think 'ke' is not necessarily needed here.
However, please note that this Indonesian sentence can have different meanings :
1) They're going to the school (building) and entering the school (building).
2) 'They're starting the school (year)' or 'They're starting at school'
The difference is not always very clear and straightforward based upon the Indonesian sentences (with/without 'ke').
I'm not sure if the following explains the difference.
Something like this :
'Mereka masuk (ke) sekolah baru'
'They enter the new school'
'They start at a new school'
I guess the difference is still vague/blurry, right !?