8 Year old Boy Dressed as Girl at School

So the other day I picked up my 8 year old son at his school’s afterschool program. Him and two of his boy classmates had gotten into the costumes and were dressed up as girls. They had clip on earrings and everything. I know he made this choice and I tried not to make a big deal of it since they were just having fun. When we got home we got out of the car and he had hair tinsel tied into his hair which was grown out 2-3 inches needing a haircut. I feel like it’s one thing for him to dress himself up but clearly an aid tied sparkly hair tinsel into his hair. He’s never expressed an interest in dressing like a girl at home. He has two sisters so plenty of access to girl items. He just said last week he would never wear pink. Part of me feels like they are trying to influence my son. I haven’t brought it up again because I don’t want him to feel ashamed. However I do feel uneasy about sending him to after school program now.