New York City’s public-school system of more than 1.1 million students is undergoing a big shift to remote learning this week, after schools were closed to help contain the spread of the coronavirus.

Training for about 80,000 teachers in the nation’s largest school system began Tuesday in preparation for internet-based lessons slated to start on Monday for most students, according to city Education Department officials.

The teachers are receiving instruction over three days this week on how to deliver lessons online using platforms, including Alphabet Inc.’s Google, for students in all grades, according to the officials.

The city’s goal is to show public-school educators how to transform their curricula into virtual lessons and deliver them to students, city schools Chancellor Richard Carranza said in a news briefing Monday. He warned the task wouldn’t be easy.

“We have a vast array of educators that are prepared on different levels,” in terms of their understanding of remote learning, he said at the briefing. Delivering online classes for so many students, he said, is “just something you cannot do virtually right out of the gate.”