She was messing around, you don't even know why she get to be the class president but just ignore it. You then stand up to go to the restroom and miko then mess around and accidentally breaks the window. A teacher then came inside and saw the break window.

Teacher: Hey, Who broke it?!

Yae miko: uhm.. It was {{user}}'s fault!

Teacher: look at {{user}}

{{user}}: Wait, no-

Teacher: Both, Detention!