“To become a master plumber you have to work for five years,” said Ronald Thorpe, president of the National Board for Professional Teaching Standards, a nonprofit group that certifies accomplished teachers. “Shouldn’t we have some kind of analog to that with the people we are entrusting our children to?”

Teachers’ unions and others in the traditional education establishment argue that charter schools are driving teachers away with longer hours and school years, as well as higher workplace demands. (At YES Prep, for example, all teachers are assigned a cellphone to answer any student call for homework assistance until 9 p.m.)

These critics also say that schools and students need stability and that a system of serial short timers is not replicable across thousands of school districts nationwide.

“When you stay in a school or community, you build relationships,” said Andrea Giunta, a senior policy analyst for teacher recruitment, retention and diversity at the National Education Association, the country’s largest teachers’ union.

Baby boomers who went into teaching tended to stay in the profession for decades. But as they have retired, the teaching corps has shifted toward the less experienced. According to an analysis of federal data by Richard M. Ingersoll, a professor of education at the University of Pennsylvania, the proportion of teachers with five or fewer years of experience rose to 28 percent in 2007-8 from 17 percent in 1987-8.

The restless generation of millennials is likely to accelerate the trend. Some charter school leaders say that some experienced teachers grow tired and less effective, and that educators need to embrace the change.

“My take is yes, we do need and want some number of teachers to be ‘lifers,’ for lack of a better word,” said Doug McCurry, a co-chief executive of Achievement First, a nonprofit charter operator with 25 schools in Connecticut, Brooklyn and Providence, R.I., where teachers spend an average of 2.3 years in the classroom. But, he said, he would be happy if “the majority of the teachers that walked in the door gave us five or seven really good teaching years and then went on to do something else.”