Les écoles (the schools) is correct.

Écoles is plural, therefore the article has to be plural too: les.

If école were singular (the school), then you’d say l’école.

You can use the singular or the plural depending on the context.

"Les écoles sont fermées"

"L'école de ma fille est fermée."

In the first case I’m writing that either all schools (from kindergarten to universities) of all kind are closed or only elementary schools are closed.
In the second case, I’m writing that my daughter’s school is closed, not saying anything about the others.