It could be that the boy had previously annoyed the girl in some way. For example, he might have said something unkind to her or taken her things without permission. So, as a form of revenge, she gave him a wedgie.
He could just laugh it off if it was all in good fun. Sometimes, showing that you don't take it too seriously can defuse the situation and keep things light - hearted.
Educate the girl about kindness and respect. Teach her that everyone has feelings and that bullying in any form, like giving a wedgie, is not acceptable.
From this story, we can learn about empathy. The boy who turns into a girl has the opportunity to step into the shoes of the opposite gender. He can feel the different treatment, the different emotional responses from others. This makes him realize that we should not stereotype genders. Girls may face some situations where they are not taken as seriously as boys in some fields, and boys may also not understand the pressure girls have in terms of appearance. By experiencing this transformation, it teaches us all to be more inclusive and understanding towards each other.
By adding some mystery. For example, the boy's transformation to a girl could be part of a bigger mystery. Maybe it's related to a strange experiment or a curse. This would keep the readers hooked as they try to figure out the cause of the transformation.
Well, it could be about a boy who discovers his true self as a girl. Maybe he starts to feel more comfortable in girls' clothes, and then gradually explores his femininity more deeply. For example, he might start to wear makeup and change his hairstyle.