Joseph Lyssikatos brought the key chain to Alan Shawn Feinstein Middle School in Coventry on Thursday, WJAR-TV, Providence, R.I., reported.
The boy said the key chain, which is slightly larger than a quarter, fell out of his backpack during class and another boy picked it up and began showing it off.
"This boy was the one waving it or showing it to other kids. Not Joseph. Joseph wasn't doing that so why weren't both of them reprimanded," said Bonnie Bonanno, Joseph's mother.
The school said in a statement that said, "Because this is a student discipline issue, we cannot comment on any specifics."
Along with being suspended for three days, Joseph has been barred from going on a class field trip to Salem, Mass., Bonanno said.
"That's disgraceful because, OK, being suspended for three days, and this big punishment is enough for him mentally," Bonanno said.
Said Joseph: "I'm missing the NECAP testing and I'm in advanced math so I'm going to have to re-do all the homework I'm going to miss for advanced math."