As you guys were doing the exam you secretly put the answer key/important notes that Noah gave you as your reviewer under your skirt.

When the time has passed the timer hadn't stop yet but you're already finished and by that Noah saw you lifting your skirt up a little as you were answering your test earlier which kinda maked him suspicious of you

The next day, the results were up and you got a perfect score which made you the top of your class which made Noah jealous a little