A KARE-TV report says the prank for last week's assembly was planned by the staff.
The winter-sport team captains were blindfolded as their mothers and fathers approached. A video posted on YouTube shows some of the kisses lasting several seconds.
One parent-child pair even moves to the gym floor, rolling around on top of one another.
In another moment of inappropriate passion, a mother moves her son‘s hand south so far he appears to grab her rear.
After the make out sessions end, the students are asked to guess whose lips met theirs.
More than lip-locks: A mother moves her son's hand south as he appears to grab her rear
Going for it: One parent-child pair moved to the gym floor as they rolled around
Unfortunate: A blindfolded student describes his mother's lips as 'luscious' before he discovers what happened
'Um, they had luscious lips, ' says one male student.
Ripping the blindfold off, he's shocked to see, not a female student - but his own mother standing in front of him, as the crowd laughs.
Mr Wollersheim said the video shows only a single minute of a 30-minute assembly, but he's not making excuses. He says the intent was to leave students feeling 'pepped', not embarrassed.
Mr Wollersheim told the network: 'This is supposed to be a fun event and it should leave everyone feeling pepped and if it's leaving people not feeling good or embarrassed or hurt then that's the exact opposite of what we're trying to do.'
Taking responsibility: John Wollersheim, apologising, said as Rosemount High School's principal, he's responsible for everything that happens at the school
Not the first time: A YouTube commenter, claiming to be a student at Rosemount, said the prank is a 'tradition' at the school
One YouTube commenter, claiming to be a student at Rosemount, called the prank is a 'tradition that only happens every six years or something.'
