A janitor found the birds before Woodbridge High School opened last month.
Eighteen-year-old Bryan Peter, Tyler Bruno and Anthony Cesareo, both 17, and a fourth student were suspended for five days. They'll also lose "senior privileges," which include attending the senior prom and walking during graduation.
Woodbridge Police Lt. Carl Lizzano told The Home News Tribune of East Brunswick they're charged with a disorderly persons offense and trespassing.
The students and their parents told the newspaper officials overreacted to the joke.
Principal Arthur Warren says he doesn't want the school day disrupted.