A job-for-life in New York City's public schools was once a near-guarantee. Mayor Michael Bloomberg is trying to change that. On July 27, the Bloomberg administration said new, more rigorous teacher evaluations had dramatically lowered the percentage of educators granted lifetime employment. “Tenure ought to be reserved for only the best teachers,” Bloomberg said. “Unfortunately, as we all know, tenure was instead awarded on the basis of longevity, not performance.” This year, however, of 5,209 teachers whose performance was evaluated by principals, 58 percent were granted tenure. That's down from a five-year high of 97 percent in 2006. “I don't know a single profession where 97 percent [of employees] deserve to get lifetime job protection,” said schools chancellor Dennis Walcott. “Tenure is now something to be earned.” Of the remaining teachers, 39 percent were given extensions, which means they are developing but have not achieved the expertise required for tenure. They will be given another year to improve before being re-evaluated. About 3 percent were denied tenure. A new four-point scale evaluates teachers as highly effective, effective, developing or ineffective. In general, teachers are considered to be on probation for their first three years, after which they are eligible for tenure. During the probationary period, the Department of Education can fire within 30 days teachers who are deemed to be ineffective. Once teachers are tenured, they can only be dismissed based on the decision of an arbitrator picked by both the Department of Education and the United Federation of Teachers. Last week, Crain's New York Business reported that in a pilot program testing the new teacher evaluations, 18 percent of teachers were deemed ineffective, while only 7 percent were considered highly effective. Filed by Jeremy Smerd of Crain's New York Business, a sister publication of Workforce Management. To comment, email email@example.com. Stay informed and connected. Get human resources news and HR features via Workforce Management's Twitter feed or RSS feeds for mobile devices and news readers.