From the BBC:
The poisonings have notably been concentrated in Qom, a city that is home to important Shia Muslim shrines and the religious leadership that forms the backbone of the Islamic Republic. Since September, the clerical establishment has been challenged by the mass protests that erupted after the death in custody of a young Kurdish woman, Mahsa Amini, who was detained by morality police for allegedly failing to wear her headscarf “properly”. Some Iranians have speculated that if the schoolgirls are being poisoned as “payback” for their role in the unrest. Social media was flooded with videos showing schoolgirls ripping off their headscarves and chanting anti-establishment slogans.
At a news conference on Sunday, Deputy Health Minister Younes Panahi said the girls had been poisoned by chemicals that “are not military grade and are publicly available”.. . . “The pupils do not need any invasive treatment and it’s necessary to maintain calm,” he added. Dr Panahi’s comment that it was “evident that some people wanted all schools… to be closed down” appeared to confirm the government believed the poisonings were premeditated.
According to the Washington Post:
In a visit to Qom on Tuesday, Iran’s health minister, Bahram Einollahi, said the poison was “very mild” and that the students’ symptoms included muscle weakness, lethargy and nausea, the Iranian Students’ News Agency reported. According to the Associated Press, some of the children described smelling tangerines, chlorine or cleaning agents. Sheikhi, the Health Commission spokeswoman, said the poison appeared to have been inhaled.
From the New York Times:
By way of background, women and girls have also led the recent protests demanding an end to the Islamic Republic, removing their mandatory hijabs, tearing the pictures of officials and chanting, “Death to the dictator.”
In response, the government has systematically targeted children and teenagers. Security agents have raided dozens of high schools and interrogated, beaten and injured students to punish them for participating in the protests. In at least one case, a teenage girl was killed during a school raid in the city of Ardabil.
But the government held an emergency meeting on Wednesday with officials from the health and education ministries, he said, and teams from the Intelligence Ministry and security forces began an investigation. “The topic of the poisoning of our dear ones was discussed,” Mr. Vahidi said, according to a video of his comments carried by state news media. He attributed some of the girls’ symptoms to stress and anxiety and blamed Iran’s enemies and foreign news outlets for causing public alarm.