"They enter those schools."

Translation: Mereka masuk ke sekolah-sekolah itu.

[Lisa-Lisa-Lisa]

why would you need " ke"?
why not mereka masuk sekolah sekolah itu

[__K.]

The preposition "ke" adds a bit of directionality and plays the place indicator. Though you can use the verb "masuk" without it, it is more idiomatic with it.

[AbdullahAAK]

it's now accepted

[Ricend_Crutis]

Why not 'pergi ke'?

[__K.]

To mean "to enter," not "to go to."