The teachers were kidnapped in Sipah area of Bara for cooperating with the polio team during the recently concluded anti-polio campaign.
The polio workers have been a constant target of the banned Pakistani Taliban and other militant groups.
Taliban has denounced vaccines as a "Western plot" to sterilise Muslims and imposed bans on inoculation.
On June 19 last year, the Taliban imposed a ban on anti-polio vaccinations, stipulating the restriction would last till US drone attacks cease.
Since then, no one in the entire area has been able to get their children vaccinated.
Accusations that immunisation campaigns are cover for spies were given credence after the killing of then al-Qaeda chief Osama bin Laden in 2012 by US special forces.
Families which vaccinated their children against polio in Bara, have reportedly been fined and threatened by militants in the past.