At 7 a.m. Wednesday, the conspirators - including a high-ranking school administrator - assumed hiding places near the office of their target: an unsuspecting guidance counselor at West Chester's Henderson High.
They held their breath as 41-year-old Kathy Teague entered a room overflowing with balloons, photos, flowers, crepe paper, and confetti.
The surprise makeover was an unconventional thank-you from seniors Shane O'Donnell and Billy Mumford and their families on graduation day - a day none of them thought would happen two years ago.
"What is going on? Who did this?" asked a flabbergasted Teague as the decorators and their accomplice, assistant principal Elisha Ozer, came forward, prompting copious tears and sustained hugs.
The threat to the boys' diplomas began the evening of June 23, 2008. Mumford was a passenger in O'Donnell's car on Burke Road in West Whiteland Township when a Chevy Blazer containing two classmates passed them. They watched in horror as the driver, 16-year-old Robert Michael Melson, lost control while turning back into the right lane.
The Blazer flipped and rolled, leaving Melson partly hanging out of the driver's window and ejecting his passenger, Casey John Russo, 16. Both boys were pronounced dead at the scene, about 100 yards from the site of a similar crash that claimed the life of William Bauernschmidt, 17, on Nov. 21, 2006.
O'Donnell's mother, Cathie O'Donnell, said her son's description of the accident for the police was so chilling that she avoided driving on Burke Road for months. She said both boys considered dropping out, and each spent his junior year at an alternative school.
But Teague remained a lifeline.
She protested that description Wednesday. "I didn't do anything but my job," she said.
Lynda Tyson, Mumford's mother, emphatically disagreed, citing numerous occasions when Teague offered needed advice, encouragement, and sometimes a safe place to break down.
"They could tell her anything, and she would always listen and help," Tyson said.
Teague, who has worked in the district for 10 years, said she could not have been responsive without a supportive staff.
"It wasn't just me," she said, a sentiment amplified by Ozer.
The assistant principal, who was assigned to the Class of 2010 in its freshman year, said "from the superintendent down," the administration values students' emotional well-being as much as their academic progress, which is why the school opened its doors to students during summer vacation in 2008 for grief counseling.
"This class has had its share of rough times," she said, pointing out that one of its 302 members is the younger brother of the 2006 victim.
"Henderson is a family, definitely - that's the best way to say it," said Carol Henson, Shane O'Donnell's grandmother.
Cathie O'Donnell said the idea to embellish Teague's office was also a collective effort, as was its execution, which the boys spearheaded Tuesday after lying in wait for Teague to leave the building.
"We discussed flowers and gift cards . . . but they seemed too ordinary," Cathie O'Donnell said.
Teague said she was looking forward to Wednesday night's graduation ceremony.
"I'm not sure I've ever been so shocked in my life," she said, smiling and shaking her head. "I love my office. It's awesome."