The schools were located in Pishin district of the province and no casualty was reported in the incident as the attacked institutions were day schools and closed at night when the attack was launched.
Police said that some unknown militants set the schools' building and the furniture inside on fire and fled the scene.
No group or person has claimed responsibility for the incident.
This is the second major incident of attack on educational institutions in Pakistan over the last few days. Earlier on Friday, some unknown militants set 12 schools in the country's north Gilgit Baltistan area on fire.