I hope your students have very simple problems. What you are talking about
is a checkbox formfield inserted using the Forms toolbar. For it to work by
clicking (a single click - not a double click - is for the document to be
protected for forms. Of course, then you can't type except in formfields.
This is what Word calls an "online form." Check this in help. For more about
online forms, follow the links at <URL:
http://addbalance.com/word/wordwebresources.htm#Forms> or <URL:
http://word.mvps.org/FAQs/Customization/FillinTheBlanks.htm> especially Dian
Chapman's series of articles.

A double-click checkbox is trickier but works in a non-protected document.
It is a macrobutton field that requires associated macros and AutoText
entries.

Go to File => New

Click on the Letters & Faxes tab and find the Contemporary Fax template.

In the bottom right of the new file dialog is a radio button letting you
select a new template or a new document (default document). Change this to
new template. Click OK.

Save your template as deleteme.dot. This template contains the macrobuttons,
the AutoText entries, and the macros you need.

Close the new template.

Open your custom template. With that open, go to
Tools => Templates and Add-Ins... and click the Organizer button.

Click on the tab for AutoText and on the right-hand side it will show the
AutoText in normal.dot. Click on the button to close the normal.dot file in
this dialog. Then open deleteme.dot in the dialog.

Copy the Checked Box and Unchecked Box entries to your template.

Next click on the Macros tab and copy the macros to your template.

Close the Organizer dialog. You no longer need the deleteme.dot file. You
can delete it whenever you want.

Where you want a checkbox, type "Unchecked Box" and press the F3 key.

If you double-click on this box, it will become checked. Double-clicking
again will uncheck it.

You can add the following macros to your template if you want a single click
to activate the checkbox:

Sub AutoNew
   AutoOpen
End Sub

Sub AutoOpen
   Options.ButtonFieldClicks = 1
End Sub

(You could add that code to existing AutoNew or AutoOpen procedures as
well.)

As you've guessed, this solution, while elegant, is complex. Hope this
helps.

Take a look at the checkbox template which can be downloaded from <URL:
http://addbalance.com/word/download.htm>.

Hope this helps,