In the end, it was just a simple box of cookies, an innocent gift to a hardworking teacher from an appreciative parent.
But investigators had suspected otherwise. So they recently barged into a classroom in suburban Seoul to open the package in front of the baffled instructor and her students.
Authorities were looking to intercept a bribe -- usually a plain envelope stuffed with cash -- given by overanxious parents seeking any classroom advantage for their children as they negotiate the highly competitive school environment.
In South Korea, the deeply rooted practice of parents offering under-the-table payoffs is known as chonji. Calling the practice an economic corruption of the classroom, authorities have announced 2009 as the year of the war against such bribes.
On a national day to honor teachers this Friday, they have devised an unusual plan: On Teacher's Day, many schools will be closed and parents will be sent letters asking them not to visit their children's classrooms for at least a month.
Investigators have also stopped teachers on the way home from school to check their vehicles for chonji-related gifts.
Such measures have touched off a debate in this education-obsessed nation about who are the real perpetrators: Are they greedy teachers with their hands out or overly aggressive parents who will stop at nothing to promote their children? Is it both?
In a recent government survey of 1,660 parents of school-age children, more than half of those polled cited parents' "selfishness" in putting their kids before all others as the main reason for the practice. Forty-eight percent considered chonji a bribe, as opposed to a harmless gift.
Accepting chonji is considered a crime in South Korea if prosecutors decide the amounts are large enough, but the law does not penalize the giver, authorities say.
"Across the country, one of five parents says they have given chonji to teachers, and one of three in big cities says so," said Kim Jong-yoon, who heads a bribery investigative team for the national Anti-Corruption and Civil Rights Commission. "This culture must be fixed and improved."
In one case, inspectors posed as parents to follow school visitors carrying envelopes and shopping bags. Kim said such tactics have brought results. One $1.50 box of candy was found to contain hundreds of dollars.
Teachers say they are often unwitting victims of a parent's neurotic drive to seek favoritism for their child.
"First of all, we do not defend or agree with chonji," said Kim Dong-seok, spokesman for the Korean Federation of Teachers. "But their investigation could get 500,000 educators condemned as a group of criminals."
Many South Korean parents consider chonji a necessary evil, an attempt to compete against richer or more influential families who already have an advantage when it comes to getting their children into the best universities.
"I gave some chonji because of the concern that the teacher might treat my kid differently if I didn't give any money when other moms did," said one parent, who asked not to be named.
Last year, South Korea passed a law that forbids teachers to ever teach again if they are fired for taking money from parents. Investigators say statistics on the number of teachers fired for the practice and the number of parents who give money are hard to come by.
Kim Dong-hee, a mother of two grown children, said she served on several school committees and favored a policy that barred parents from the classroom on Teacher's Day.
"Competition in college entrance exams is too intense here," she said. "And teachers' subjective evaluations are more influential than objective tests. It is a culture of give and take."
Chonji don't always come in the form of cash. Sometimes parents sponsor school events or invite the teacher to lunch or dinner without the knowledge of the school.
Some teachers make no excuses about accepting chonji. A parent wrote a letter to a Seoul newspaper claiming that she had offered a teacher a gift worth $70 and that the teacher had suggested that it was not enough, saying, "I can only get a pair of shoes with this money."
In light of the new government vigilance against chonji, many parents are finding new ways to ingratiate themselves with teachers, investigators say. Some send the bribes by online shipping or express delivery to avoid the long arm of the law.
Park is an assistant in The Times' Seoul Bureau.