When in Rome ...
Though these school sites undoubtedly do many things wrong, and are
often totally unnavigable, the degree to which each one looks like the
other seems consistent with one of Jakob Nielsen's Good
Deeds in Web Design:
Do the same as everybody else: if most
big websites do something in a certain way, then follow along since users
will expect things to work the same on your site.
So even if it's by default, there may still be something positive about
them.