Hey, that's MY system! (Kidding . . . . in mine, it's on the right. :-)
There are about a million and a half ways to do this. :-) I'll suggest the first that comes to mind.
Once it's all working, you have a page template for the administration area, and in this template you specify
In the .js file is all the stuff that assigns the menus and their respective links to the admin menus. I'll leave off there on that part, you can use Ajax or "grow your own" menus, depending on what you find easiest to learn. Likely you will only have to do one thing to the script you've developed, add ID's to the links:
<li><a href="script.php?res=students" id="student_link">Manage Students</a></li>
<li><a href="script.php?res=instructors" id="student_link">Manage Teachers</a></li>
<li><a href="script.php?res=holidays" id="student_link">Manage Holidays</a></li>
(Depending on how you implement your menus, you may NOT need to add the ID's. You may just have to point the JS at a class or ID just the <ul> - as I said, about a million and a half ways . . . )