drupal Q: how to allow content access to logged in users only?

hi all,

on a drupal is 7.8 site:
i have a menu that has some pages that are open to all (anonymous users).
i want to add on this menu some pages that only registered (logged in) users can see.

how do i do this?

what i've managed to do is create a block with a menu that only shows after login, but the pages in this menu are still open to all (if someone types their url, he can reach them, so its not related to a menu link or not).

please help? i've spend 2 days on this.

User permissions will do this. Just change which pages they can see, its very easy in Drupal. I have a school site setup where no one can see the tests but the students.