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I don't know of a way to do this in word. Only way I know to accomplish this in word is to select all the answers, leaving the ans) portion. Hit delete, and print the page. Once it starts printing, you can use Ctrl.+Z to undo the deletion and then print the parents copies. Or, if you've saved a copy of the doc., you could print the parents page then select (hold down ctrl to multiple select) and delete the answers/print the students copies and when you close the doc. don't save the changes.
Hope this helps.