Cassie,
If you are allowed/permitted to offer a more complete view of CO2′s role in things- at your daughters class- I suggest trying to help students improve their knowledge of the Carbon Cycle. Something is amiss if only 8% of college students understand that the mass of a tree comes from CO2 (see question 6 in the attached file).
“College Students’ Understanding of the Carbon Cycle: Contrasting Principle-based and Informal Reasoning”
http://news.msu.edu/media/documents/2011/01/f6e8a4d5-8ccb-48be-8d4b-1915c5c2583c.pdf
In my 5th grade science class we ran the famous mouse in a jar experiment. It’s hard to call a trace gas evil if plant life uses it………
http://environment.nationalgeographic.com/environment/enlarge/jarmouse.html