How do I touch my teacher's butt without them feeling it?

I am staying after school with my teacher to finish a homework assignment. Fellas how do I slightly place the palm of my hand on the bum without the teacher really feeling it?

At the end of my literature period, a lot of boys had gathered around my hot teacher to ask her something or the other. Quite a crowd. Strangely one boy was standing right behind her. The last bit of her hair sometimes flew in his face but he didn't move away. A few seconds later his hands (which were first curled into fists) became curved. It seemed he wanted to touch her butt with his palm. But the teacher probably had a class after that.She broke through the crowd and was going away. He fast walked after her, touched her butt very lightly with his fingers and started asking her a question (probably about going to the washroom or something) and at the end went back to his seat. I don't think the teacher had noticed him touching her butt (he probably touched so lightly). So my advise is to do it in a crowd or the way the boy did. Hope this helps!

why would you want to touch your teacher's butt?

I do it by just like putting my hand back and gently grab it and then this one time she flashed the back top of her white panties and I touched her ass and pulled on the panties