Tanzania's President John Magufuli has been condemned for comments that girls who give birth should not be allowed to return to school.
An online petition has been set up and a pan-African women's organisation is mobilising to get the president to apologise and reverse his comments.
Mr Magufuli warned schoolgirls at a rally on Monday that: "After getting pregnant, you are done."
A law passed in 2002 allows for the expulsion of pregnant schoolgirls.
The law says the girls can be expelled and excluded from school for "offences against morality" and "wedlock".
Women's rights groups have recently been urging the government to change the law.
Mr Magufuli, who was speaking at a public rally in Chalinze town, about 100km west of the main city Dar es Salaam, said that young mothers would be distracted if they were allowed back in school:
"After calculating some few mathematics, she'd be asking the teacher in the classroom: 'Let me go out and breastfeed my crying baby.'"
He said that men who impregnate the schoolgirls should be imprisoned for 30 years and "put the energy they used to impregnate the girl into farming while in jail".
'I was a teenage mother': Jackie Leonard Lomboma, who runs a centre for teenage mothers in Morogoro
I had just finished my primary education; I was supposed to go to secondary education but could not afford the fees.
I met this smart boy, who promised that he would ask his parents to help me go to secondary school if I agreed to be with him.
I didn't date him, like girlfriend and boyfriend.
The first time I met him was the first time I got pregnant and that was the last time I saw him.
Because I was kicked out of school, my grandfather chased me out of home.
I eventually found work as a maid. When the family left, they asked me what I would like as a goodbye gift.
I said I wanted to go to school. It was a shock but they eventually agreed.
It is a big disappointment to hear such a statement from our president. It is only education which can help any country in this world overcome poverty.
President Magufuli also criticised rights organisations who have been pushing the government to reverse the law:
"These NGOs should go out and open schools for parents. But they should not force the government [to take back the pupils].
"I'm giving out free education for students who have really decided to go and study, and now you want me to educate the parents?"
The BBC's Sammy Awami in Tanzania reports that the crowd at the rally applauded the president's comments.
At least 8,000 Tanzanian girls drop out of school every year due to pregnancy, according to a Human Rights Watch report.
The online petition says that the president's support for the expulsion law would end the education of many girls and "propagate more discrimination".
It instead calls for the girls to be protected from early pregnancies while in school.
The African Women's Development and Communication Network, Femnet has also expressed its outrage.
"With all the work we have done to emancipate Africa's girl-child from the shackles of discrimination and violation, a sitting president turns around to "re-victimze" and treat their situation like a terrible infectious disease which other girls must be protected from," said its head Dinah Musindarwezo.
Lawyer Kavinya Makau called Mr Magafuli's sentiments a" betrayal of the highest order."
Two weeks ago, Tanzania's Vice-President Samia Suluhu called for young mothers to be readmitted to school, saying they should not be denied a right to education.