conditional formatting based on text in different cell???

Hi All,
I might be trying to do something that is totally not possible but I have tried but have been unsuccessful. I creating a spreadsheet for my wife pre-K class to help speed up daily reports to the parents.
I have a dropdown boxes that is pre-populated with some comments via Validation data from a separate worksheet. Simple enough but I am trying to automatically change a cell next to it with some sort of visual image from conditional formatting like a green check or a red 'x'. So if the she picks "Student was bad" the cell next to it puts a red 'x' (bad) and if she picks "Student was good" it puts a green check.

Please let me know if this needs further explanation.

Thanks in advance,
John