Celebrations culminate in a parade of open-air trucks driving through Finland's biggest cities.
Often dressed in costumes, final-year students stand on top of decked out lorries shouting slogans and throwing sweets at crowds. It's also a party day for students.
Seniors now have around a month to prepare for exams, which start in March.
Penkkarit, more formally penkinpainajaiset, ("bench pressing") refers to the hefty studying sessions school-leavers face as they review all of the material of their high school careers in preparation for the matriculation exam.
