If you teach High School then you should at least know that humans are a carbon based species. We emit carbon and we consume carbon. Without enough carbon we would die. So "making a smaller carbon footprint" would require mass genocide or suicide of all living things. You might want to let those kids in the classroom know that instead of parroting popularized nonsense.
Wow, you are kidding right? Harsh, unnecessary, and, in that tone, you do realize that "smaller" is a relative qualifier?