Sad frustration

My son came home with a mix of sadness, anger and frustration today.
He's not very good at maths and sports, does things at his own pace (read: quite slowly), and on top of that he has a kind nature - which makes him an easy target for teasers. Today he was teased by the worst teaser, a highly intelligent but also highly arrogant girl.
On days like this, seeing this look on his face, I wish schools were never invented.