Participation. Always having the right answers. Helping others. Spying the grades when papers are handed back. Never complaining about low grades. Showing no signs of stress or worry about exams. Asking questions for more information not already discussed or immediately relevant to the topic under consideration. The way a student carries on conversation. Being asked what grade s/he earned and divulging that information.

I went through many schools as a child. I never bragged about my grades. Everyone always picked up on me being a straight-A student very quickly.

Praise from teachers. Other visible signals, like reading voluntarily, showing interest in challenging work, etc. I agree that bragging isn't really part of being a nerd.

Teachers talk in class when they shouldn't.

"Hey Teacher, how much is the curve on this test gonna be?"

"Well, it won't be anything because John got a 100."

[Angry glares at John]

You go to a school where the grades are read out loud or published in some form.

This isn't unique to the Middle East. Its often no secret who the valedictorian of your class will be in my experience (American school)... even if the grades weren't revealed.

In any case, "Nerd" in my experience means something closer to the hobbies you persue. "Geeks" play video games and academically do good in "computer stuff" and music. "Nerds" pursue theater, LARP, and table-top RPGs (Dungeons and Dragons, Pathfinder, World of Darkness, etc.)

The intersection of "Nerds" and "Geeks" is anime, comic book heroes, and sci-fi.