Five of the six trailers at the school on Roosevelt Avenue and 98th Street were installed in 1994, and one has been used since 1987 — and parents, teachers and students have complained for years of the conditions inside, including inconsistent heat and air conditioning.
Some 500 of the school's nearly 2,000 students took classes there.
The Corona school's extension is part of a citywide plan to add thousands of seats to the school system in the coming years.
Borough President Melinda Katz, who announced the removal of trailers in her State of the Borough address, said the trailers were just "Band-Aids" that never created a permanent solution.
"Our families and kids deserve better resources," she said.
MORE SCHOOL COVERAGE FROM DNAINFO
It will take nearly two years for the trailers at P.S. 19 — the largest elementary school in the city with 1,909 students as of 2012-'13 — to be removed, officials said.
The trailers should be gone by summer 2016, months after the design process for the school's extension begins. The addition is expected to be completed by 2019.
During construction, 500 incoming students will be temporarily relocated to P.S 315's new building on 43rd Avenue. That school has not yet opened.
Pols and activists have worked for years to get the trailers removed, and they gathered with parents and community activists in the freezing cold to declare the plan a victory.
Rafaela Vivalo said her son, now in second grade, was upset about going to school in the trailer when he was in kindergarten.
"He had to learn in a trailer and was always cold and wet during the winter, his feet never had enough time to dry," since they traveled outside throughout the day, she said.
Now the kids will get "the space that they deserve."