Dartmouth High School students had quite the surprise when they arrived for classes on Valentine's Day and found thousands of sticky notes covering every locker in the building.

Jessica Lassey, a teacher at the school who shared videos and photos of the display on social media, said approximately 2,000 notes in total were posted, each containing a positive message for its reader. They were posted by a person who still remains anonymous.

She listed off several post-it notes she saw, which displayed messages such as "You're beautiful," "You're radiant," and "You're unique."

"They were all encouraging, neutral messages. It was just about the core person. They could have been for anyone," she said.

Throughout the day, students carried the post-it notes along with them, sticking them to their water bottles, the backs of their phones, and their desks.

"I've never seen anything like it. It's such a selfless act," Lassey said, adding she's been teaching for 10 years.

She said it provided a breath of fresh air for students who might have a bad memory of Valentine's Day, providing students with an uplifting message.

"Every single kid in the school had a note to greet them," she said.

Lassey said the biggest mystery for staff is how someone managed to pull everything off. Each note was handwritten by the same person. Lassey said she was in the building for a volleyball event late into Monday evening and did not see anything out of the ordinary, but everything was in place by the start of school the next morning.

Principal John Gould said he was not sure who is behind the display, but it appeared to be well received.

"Students and staff were happy about it," he said.

The notes were up throughout the day on February 14.

Video courtesy: Jessica Lassey/ Facebook