0 looks way too big to me to be in that row. His shoulders measure almost as wide as the teacher’s in the top right. His head is similar in size to the ones in the front row but much larger than the children in the 3rd. And compared to the boys in the back row, he’s a giant! It’s a really strange looking picture.
I am not an expert in voice but I do have 30 years of extensive headphone use and at one time did have perfect pitch so I have a general idea.