The accident occurred in southern Poland, roughly ten kilometres from the town of Legnica. The bus veered off the road and into a ditch, coming to a halt on a 45 degree angle.
"We are all shocked, one of us is seriously injured and four have minor injuries," Thomas Zätterman from the Kulturskolan in Jönköping told the Aftonbladet newspaper from Poland.
The group of teenagers was heading to Slovakia to perform as part of an orchestra group, with most of the passengers aged between 15 and 17, the paper reported.
The injured adult, the driver, was rushed to hospital via helicopter.
It remains unclear what caused the accident.