Juan, you can certainly cut off access to quizzes and such by setting a closing time, although if you want students to have access the following day again, you'd have to set manually, to the best of my experience.
My bigger concern though is, why would you want to restrict access to only during the school day??? That seems to defeat the purpose of using Moodle in the first place. You might think about what you don't want students to do after hours and lock that down, but in my work we use Moodle in part as a file
server, delivering information on what to do by when to the students, and I want them to have access to that all the time (and their parents, too, depending on the age of the student).
