Apache: One setting for multiple directories

DirectoryMatch also works

<DirectoryMatch ^/var/www/(adminer|school-project)>
...
</DirectoryMatch>

try this

<Directory /var/www/>
   ... auth_digest settings
</Directory>

Regex can be used with Directory directive.
http://httpd.apache.org/docs/current/en/mod/core.html#directory

If you just want to protect some of them, I think this should work.

<Directory ~ "(adminer|school-project)"/>
   ... auth_digest settings
</Directory>

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