Only 55 percent of eligible teachers who worked for three years earned tenure in 2012, compared with 97 percent in 2007.
The policy shift marks the culmination of years of work toward achieving New York Mayor Michael R. Bloomberg's goal of ending "tenure as we know it," The New York Times reported Saturday.
Forty-two percent of teachers were kept on probation for another year and 3 percent were denied tenure and released, the Education Department said.
The totals demonstrate a shift in how tenure is determined in New York and across the country, the Times said. The sluggish economy has crimped spending for new teachers, and U.S. grant competitions that encourage states to change their policies prompted lawmakers to tighten requirements for earning and keeping tenure.
"There has been a sea change in what's been happening with the teacher tenure laws," said Kathy Christie, an official with the Education Commission of the States. "In 2011 there were 18 state legislatures that addressed some component of teacher tenure and many of them in a significant way, and that is enormous."
In New York and many other school districts, tenure is becoming increasingly based on students' standardized test scores and mandatory classroom observations by principals or other administrators, education officials said.
"It is an important movement because what we know is that when schools improve, a lot of the improvement relates back to having really strong teachers organized around a common vision," Shael Polakow-Suransky, the city Education Department's academic officer, told the Times. "I think New York City has some of the best teachers in the country. ... But we also want to keep pushing them, just like we want to keep pushing our kids."