The Customize Toolbar dialog can be accessed by selecting Customize Toolbar... from the Logger Pro menu.
This is one of the few features in Logger Pro that is unique to Mac OS X. To add an available button to the toolbar, drag it from the list of buttons onto the toolbar at the top of the screen. To remove buttons, just drag them off of the toolbar. For example, if you would like to make the curve fit button unavailable to students, you could drag the curve fit button off of the toolbar.
Note that this setting is specific to the user who is logged in. If each student has their own login name, the change will need to made to each user.