An eighth-grader suspended after pranking a classmate with a bag of oregano following a lecture on the dangers of marijuana has a civil liberties group in his corner, but officials at his North Carolina school aren't backing down.

The boy was booted from his school for 55 days for the stunt at Cuthbertson Middle School in Waxhaw, N.C. School officials cite the district's policy manual, which says a student can get a 10-day suspension for "possessing illegal or counterfeit drugs and "misuse of chemical/material (organic or otherwise) that causes or is purported to cause a hallucinogenic/mind altering effect." A longer suspension can be imposed if officials determine a student's conduct "demonstrates a willful violation" of school policies.

"It was just a joke," the mother of the boy, who is not being identified because of his age, told FoxNews.com in an exclusive interview. "He's embarrassed that it's turned into such a big issue. He's actually said he doesn't know why he did it. But he didn't have an illegal substance to begin with."

Luan Ingram, a spokeswoman for Union County Public Schools, confirmed to FoxNews.com that the matter was handled according to its student discipline policy, but declined additional comment.

In a letter to Union County Public Schools officials, the Virginia-based Rutherford Institute called the suspension a "gross overreaction" to a childish prank and said it may be a violation of the boy's constitutional rights.

"We want the record cleaned up so this doesn't track him for the rest of his life," John Whitehead, president of the Rutherford Institute, told FoxNews.com.

Immediately after the incident last month, in which the boy passed the bag of seasoning to a pal a day after their health class discussed marijuana, the boy received a 10-day suspension. On Feb. 1, school officials notified the boy's family that he had been recommended for another 45 days of suspension. Their appeal of the additional term was denied this week, and the boy is attending a school for at-risk students until he is eligible to return to Cuthbertson on March 29.

While Ingram refused to discuss whether the boy has had prior disciplinary issues, his distraught mom said he's never been in serious trouble. He has been punished for minor infractions, she said, including chewing gum on the bus and roughhousing on school grounds.

"Nothing serious, all kid's stuff," she said, adding that this is the first time he's been suspended.

Whitehead said oregano cannot be considered a "counterfeit or synthetic drug" since the term is not defined in the district's policy manual and doesn't fit the statutory definition in state statutes. That violates the kid's due process rights, Whitehead said.

Whitehead noted recent North Carolina legislation requires local school boards to minimize use of long-term suspensions and expulsions to violations deemed to threaten safety of students, staff, or school visitors or threaten to substantially disrupt the educational environment.

"Your school district would be hard-pressed to demonstrate that [the boy's] conduct either threatened the safety of the school community or substantially disrupted the school environment," Whitehead's letter to the school district stated.