At Bronx Lab School in Williamsbridge, students studying for the United States history and government Regents exam took special prep classes and came in for extra help on Saturdays. At Millennium High School in Manhattan, administrators found money in a tight budget to pay for Regents test tutoring after school.

But for those students, and tens of thousands of others who fell asleep on Wednesday with their No. 2 pencils at the ready, weeks of preparation ended with a fizzle. Snow closed all New York City schools and forced the cancellation of Regents exams in six subjects citywide on Thursday, putting more pressure on students facing an already packed schedule of exams in June.

“It’s sort of like practicing for play for a month of two and then finding out that the production has been delayed for five or six months,” said Robert Rhodes, the principal of Millennium High School. “Everyone has to keep practicing.”

It is unclear exactly how many students would have taken the Regents in the city on Thursday, because the city only tracks the number of exams requested by schools, a higher number. Schools asked for 46,000 exams in United States history, 22,000 in geometry, 9,000 in chemistry, 1,800 in physics and 18,000 in skills tests for special-education students.