A high school student spent nearly six-months making 1,300 heart-shaped Valentine's Day cards for every single one of her classmates.

The anonymous cupid taped an origami heart with a handwritten message saying “you are loved” to each of the student, teacher and staff lockers at the Troy High School, in Ohio.

The teenager started to make the hearts in September and had been storing them in her closet at home to keep them a secret.

School principal Katherine Weaver, told The Independent: “To have someone so dedicated to every single person in this building — that’s just an amazing quality for anybody to have, especially a high school student.”

She added that she had spotted the student and a few helpers pasting the hearts one by one on all the school’s lockers, the night before the big day.

"First I wasn't sure what to expect and what the notes on the lockers were," she said. "But when I saw what they were and saw rows and rows of the paper hearts it was quite overwhelming. I was really excited to go home and know that the students would find the hearts in the morning."

She added: "When they did, it was amazing — after the first hearts were found, they all went to check if they had something on their locker to bring home. I know the student just really wanted to make sure everybody had something on Valentine's Day and that they all felt part of a collective and felt they were loved.

"We are so proud of out wonderful students."