Pizza party and free time after admin observation?

I had an observation with one of my periods yesterday at a middle school. I told the students if they did their best they’d have free time and id buy pizza for them.

My coworker thinks it’s unprofessional and that I’m bribing them (which I can see), but also if I have a bad observation that could affect my livelihood. What is your take on it? Does anyone else reward their students?