Student "grades" an apology letter from his ex-girlfriend. It does not go down well.

A 20-year-old student in the US has “graded” an apology letter from his ex-girlfriend. The letter, along with his annotations and a final mark of 61/100 has gone viral.

“We started dating in February of last year and dated for about eight months,” Nick Lutz from the University of Central Florida told the BBC. “Four months in she started hiding her phone and I heard she had code names for guys in her contacts list.”

The letter is seemingly honest and heartfelt.

“It’s hard to imagine there is nothing left of us,” his ex-girlfriend has written. “I saw you the other day and I couldn’t help but cry.”

Lutz was not moved.

“Too long of an introduction and lots of repetition,” his red pen says. “Also, no [paragraph] indents.”

When your ex writes you an apology letter so you grade it to send it back pic.twitter.com/MczdjcCiil

— Nick Lutz (@NickLutz12) February 17, 2017

She apologised for not holding up her end of the bargain.

“How? Need reasoning here,” Lutz has written.

She says she never cheated on him. Even “promising on everything” that she remained faithful.

“Strong statement, no supporting details,” Lutz wrote. “Need details to support your hypothesis.”

She says she has "no reason to hide, lie or hold anything back".

"If there is no room to lie, why isn't the truth being told?" he asked.

And then there's this...

"Part of you will will remain in my heart. I just hope to God you have thought about me," she wrote.

"I have not," his red pen reads.

Lutz meant the annotations to be a joke between him and his friends. But it's turned into much, much more than that.

The pictures of the letter, posted to Twitter, have been shared more than 100,000 times.

"She's not the happiest but I didn't expect it to go viral," he said. "She still speaks to my mum."

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Lutz told the BBC her letter wasn't going to change anything.

"[The relationship] came to an end after she told me she was going to a theme park with her best-friend who's a girl but I later found out she went with a dude," he said.

"I haven't spoken to her since this happened but I am not planning on talking to her anytime soon."

He has, however, encouraged her to try again, as "revision for half credit will be accepted".

His parting shot? "Good luck" and a D-.