The four women had created an informal admissions support group, complete with a shared Google calendar, a robust group text and the promise of company on long waits to tour schools. “We’ve been going through hell,” Ms. Kriegel said.

“The Department of Education should be doing what Elissa Stein is doing, for free,” said Jill Taddeo, who was part of Ms. Kriegel’s crew.

Ms. Stein said about 500 families have signed up for her newsletter this fall, but noted that about 80,000 students are currently applying to high school. Ms. Stein said she offers reduced rates to low-income families and has signed some people up for free. “It shouldn’t be this hard to go to high school,” she said.

Under a school choice system created by Michael R. Bloomberg when he was mayor, the city allows students to apply to up to 12 high schools anywhere in New York , and an algorithm matches children with one school. Some parents said the ranking process was so daunting that they turned to YouTube for strategies.

Though there is no penalty for students who do not attend a tour, Beacon’s two open houses provide the only opportunity most families have to see inside the school. The Department of Education said that school also organizes small student tours that are not advertised.

Beacon, unlike Stuyvesant, does not have an admissions test. But to win a spot, students must have high standardized test scores and grades, along with a strong portfolio of middle school work and admissions essays. Students are much less likely to be accepted if they do not list Beacon as their top choice.

A teacher at the school, who spoke on the condition of anonymity, said some at the school believe that enrollment, “reflects income, and where kids grew up, and not necessarily academic ability.”