YA sci fi boy finds out classmate is an alien

[Cassandra]

I don't remember a lot about this book so I apologize. I read it when I was around middle school age. A boy finds out his classmate (maybe a friend but could be an enemy) is an alien when he goes to his house. I remember an important scene happening when they were in a science lab. The plot might be he has to stop him from destroying society. I think he was investigating him because he accidentally witnessed something strange and then tracked down where he lived. Inside his house may have been people he was doing experiments on. It also may have been from a series of books with different mysteries. Thank you. I hope that was useful information.

[Kris]

A long shot - Stuck on Earth on David Klass?

Cassandra, around what year did you read this book? This will help narrow down the search.

What's the tone or genre - funny/silly, mystery, action, thriller, etc?

[Marie]

Long shot but I Am Number Four?

[Summer]

Sounds like Bruce Coville's "Aliens Ate My Homework" series. His classmate is an alien, and keeps his robot 'parents' in the closet when he doesn't need them.
https://www.goodreads.com/book/show/3...

[Lobstergirl, au gratin]

Cassandra, are you still looking for this or did you find it?