Annette Renaud was riding the C train last weekend when a man approached and asked to take her picture. It was Brandon Stanton, of the popular website Humans of New York, and as usual, he asked what was on her mind. That’s when Ms. Renaud, a parent who is on the School Leadership Team at the Secondary School for Journalism, a high school housed in the John Jay educational campus in Brooklyn’s Park Slope neighborhood, let loose.

She was upset, she said, because students at the school who were trying to qualify for their Advanced Regents diplomas were being undermined by the school’s administration. The advanced diploma requires three years of language study, and the principal at the school had gotten rid of the Spanish teacher at the end of last year and had not replaced her, leaving seniors at the school in the lurch.

“We’ve got a new mayor and a new chancellor,” Ms. Renaud continued. “So we aren’t blaming them. But they need to know how impossible they’ve made it to help our kids. Trying to get something fixed in these schools is like praying to some false God. You call and email hoping that God is listening, and nothing happens.”

Someone was listening. The post immediately went viral, with 150,000 likes on the Humans of New York Facebook page, it was shared more than 16,000 times, and it had strangers from across the city and the country pledging to call the school in protest on behalf of the students. Someone in Michigan started a change.org petition calling on the school to hire a foreign language instructor; another Connecticut petition asked the Department of Education to help the students — it has more than 1,000 supporters. People posted the school’s email address and phone number and some later reported that their emails were bouncing back because of the volume of correspondence.