Bad reports at daycare

Hey mom's Just wondering if anyone else is going through bad behaviors in preschool? I'm currently having conversations with him about making good choices and listening to his teacher. I've even started a reward jar that he can put a pom pom in if I get a good report at school and then if we have five good days we can do something special on the weekends. That seemed to work for awhile, but he recently had two bad days. He is also obsessed with this other little boy in his class and the two are trouble makers together. I had a conversation with the teacher last week and she said he knows how to make good choices because when that friend was gone all last week he was an angel. I found a YouTube video about making good choices and we watched it together today. I really don't know what else to do. Looking for guidance or ideas to help my sweet boy. Thanks so much.