Police will give extra protection to the workers taking part in the campaign in Peshawar, Nowshera, Charsadda and Mardan, said the commissioner of Mardan, Adil Khan.
Many local residents view the girls' primary school and medical clinic run by the NGO at the community center as saviors for the community's poor. Now many are worried about what will happen if those services are cut off.
Gul Afzal Khan, a villager whose children studied at a community center run by the group, said the attack was a big loss.
"What is their crime?" he asked. "They were just giving free education and health assistance to our children."
The attack also was another reminder of the risks to women educators and aid workers from Islamic militants who oppose their work.
Last month, nine people working on an anti-polio vaccination campaign were shot and killed. Four of those shootings were in the northwest where Tuesday's attack took place.
Associated Press writer Riaz Khan in Peshawar contributed to this report.