maybe they can provide some insight to this better than what I could.
I'm so sorry this is happening to your daughter. I know I was teased terribly when I was in the 4th grade because I was so dark. That was the first year we had colored pictures at school and I had on a yellow dress in the picture which didn't help much.
I agree with the others that you should probably talk to someone at school or the boy's parents with your daughter's permission. She may not want you to speak to anyone about it.
Let us know what happens. I hate to hear of a child being teased.