Rihanna made 2,500 young fans wait for four and a half hours for her to arrive at their school after they won a contest sponsored by her.The 'Stay' singer has come under fire for appearing at Barrington High School in Chicago extremely late and staying just 16 minutes after the school won a competition, sponsored by her, by producing a video highlighting their charity work and using her hit song 'Diamonds' as the soundtrack.According to The Chicago Tribune the 25-year-old star was supposed to be at the school at 1pm on Thursday (21.03.13), but she didn't turn up until well after 5pm.The students were allegedly forced to wait inside a small gym until she arrived.Rihanna suggested traffic was the reason for her lengthy delay, as she tweeted on her way to the event: "This Chicago traffic is not working."But she allegedly made no apology or gave any explanation for her lateness upon arriving at the school and simply told the students: "Thanks you guys for coming and waiting," however she gave out some free tickets to her show.Patricia Halle was one of number of students to complain, saying: "It's one thing to be fashionably late. This is just rude. Our lives don't revolve around a pop star. Our school worked hard to win this. She should be more respectful."After leaving the event, Rihanna tweeted her support for the school, writing: "Barrington High School (BHS) Facts. They raised 40 thousand dollars for Joplin Missouri after the tragic tornado hit Missouri in May last year"#BHS #facts they participated in the relay for life for the American Cancer Society and raised $700,000"#BHS thank you man!!! You guys RULE!!! I love this school!!! (sic)"The star was also previously unapologetic when she made fans wait two hours for her to grace the stage on her "Diamonds" world tour in Montreal, Canada on March 18, 2013 because she was still suffering from laryngitis, which forced her to cancel two other shows.