President Obama made another push for his education agenda last week, with a renewed call to hold the worst teachers accountable.

Those who fail to improve quickly have "got to go." It is a harsh directive, but a necessary one, given the sorry state of public education. Students are failing classes and flunking out at alarming rates — unable to read or perform basic math skills.

Obama's plan calls for teachers who miss the mark to get additional training and a chance to improve, which is fair. But those who still fail to improve after a reasonable period could be fired.

No doubt, teachers' unions are disturbed to hear such tough talk again from Obama. But the president has made clear his intent to change the status quo.

Obama did express his desire to work with the education unions. Historically, collective bargaining units have been reluctant to address issues such as tenure that make it difficult to get rid of poorly performing teachers.

That must change. Keeping bad teachers who wear tenure like a badge of honor hurts students in chronically troubled schools. It also makes it difficult for good teachers to create environments where students can succeed.

Rather than rise up in knee-jerk opposition to the president, unions should continue to work with the administration to make needed changes that will be in the best interest of students.

These reforms include rewarding the best teachers with merit pay, closing the lowest-performing schools, and giving students more alternatives when their neighborhood school is bad.

The president was on point in calling for higher standards for students, who too often become victims of low expectations. He also rightly acknowledged that more money alone will not fix the public schools' problems.

Obama announced plans to recruit 10,000 teachers in science, technology, engineering, and math over the next two years. Emphasizing these disciplines will better prepare students to compete in a global economy.

Obama also endorsed extending the school year. He offered no specifics, but the idea makes sense. Giving students more time in the classroom would bring the United States in line with Asian countries, where students are performing better academically.

The president has set the right priorities for overhauling America's public schools. To pass the test, he wants to put more good teachers in the nation's classrooms so every student will have a better chance to succeed.