Two of the girls targeted sustained injuries to their back, while one received a cut to her brow during the attack in the city of Zielona Góra, according to state news agency PAP.
Their injuries are not life threatening, police said.
Małgorzata Barska from a local police headquarters in Zielona Góra, said: “The 16-year-old probably took two knives from home. At school, she used them to injure three random girls."
Barska added: "The perpetrator was overpowered by teachers and shortly afterwards handed over to police officers called to the scene.”
According to a local news website, other students said the 16-year-old attacker had posted entries on social media warning that there would be “slaughter” at their school.
(pk)
Source: PAP/IAR/Polish Radio