"I couldn't focus on schoolwork because I was focused on surviving."
Rapman is talking about his childhood growing up in South London ahead of the release of his debut film, Blue Story - a tale of friendship, love and postcode wars.
It follows the life of Timmy who lives in Lewisham but goes to school in Peckham - two areas that have a notorious rivalry.
Rapman - real name Andrew Onwubolu - tells Radio 1 Newsbeat: "That part of it was based on my life - it made my school experience very difficult."
The film's message is backed up by its soundtrack, with lyrics like: "I'm not trying to justify, I just want to show you what these young boys are fighting for."
Rapman says he wants the audience to see past crime statistics and headlines about knife crime, to understand how a "good kid" can lose their way.
"I want people who see the film to learn that these kids are not all spawns of Satan.
"They didn't come from child abuse or neglectful mothers. What kids go through in the school playground is so intense, it all starts there."
He believes that more provisions should be put in place to support children who have problems at school, and mentoring should be given instead of "waiting until they're 17, feeling alone and end up picking up a weapon."
The rapper-turned-film-maker's work first went viral in 2017 when his YouTube series, Shiro's Story, amassed more than 20 million hits.
The three-part drama tells the story of a character whose world is turned upside down when he gets involved in drug dealing and violence, while coping with the news his best friend is the biological dad of the daughter he thought was his.
The story is told mainly through music, Rapman's bars to be specific, and it got him noticed by Jay Z, who signed Rapman to his label RocNation in 2018.
After the success of Shiro's Story, the rapper was able to start work on the film script he had been sitting on for a while. He worked with the BBC and Paramount Pictures to make Blue Story.
"My casting director went to all the top agencies to find actors but I also wanted to use raw talent.
"I put a casting call out on social media, I wanted new faces."
One of those new faces was Stephen Odubola.
Stephen, 23, emailed Rapman after Shiro's Story won an award, saying he would love to work with him - but got no reply.
A few months later, after trying his luck at the open audition, he was cast as the one of the lead roles in Blue Story.
Stephen tells Radio 1 Newsbeat: "I walked into that audition and didn't think I would get it. There were so many people.
"I prepared so much, and now watching it back is like an out of body experience. Watching the greatness we have created."
Rapman is clear that Blue Story, which also stars Top Boy's Micheal Ward, is a film for everyone.
"Mothers, kids in gangs, kids who aren't in gangs, politicians.
"It's the most authentic journey you're going to see.
"I love when I go to the screenings and see people who look like they've had no connection to that world - people who are upper class, wealthy, and are just curious.
"I'm hoping that everyone who can't relate to that world, but understands human emotions, goes to watch it."