Police in Poland detained 76 people. They also checked nearly 50,000 schools.

Both steps followed two school attacks. The effort aims to prevent more violence.

Reports describe the attacks as knife attacks. They happened on back-to-back days in northeastern Poland.

The attacks left one person dead and several wounded. Some of the wounded were children.

Reports say a 15-year-old killed a school janitor. The attacker also wounded two others at the teen's former school.

Some schools suspended classes on Friday. Some parents kept children home. Police patrols were sent out.