The attacker, a 21-year-old female student at the school, was arrested by police, Polish news channel TVN24 reported. One of the victims was taken to hospital with non-life-threatening injuries, while the other two sustained minor injuries, Xinhua reported.
On Wednesday, a 19-year-old student injured nine people in a knife attack at a school in Ostroleka, in central Poland's Mazowieckie province.
A day later, a 15-year-old boy stabbed a school principal, a cleaner and a teacher at a school near Wyszkow in the same province. The 37-year-old cleaner later died of her injuries.