WASHINGTON — President Barack Obama today embraced a new approach to public education that adds up to merit pay for the better teachers and longer days and school years for students.

These proposals, which constitute the new president's vision of an education system that meets 21st century challenges, are sure to generate loud criticism, particularly from teachers' unions.

Educators oppose charter schools because they divert tax dollars away from traditional public schools. Merit-based systems for teachers have been anathema to teachers' unions, a powerful force in Obama's Democratic Party.

Obama acknowledged this in his talk to the U.S. Hispanic Chamber of Commerce.

"Too many supporters of my party have resisted the idea of rewarding excellence in teaching with extra pay, even though we know it can make a difference in the classroom," he said. "Too many in the Republican Party have opposed new investments in early education, despite compelling evidence of its importance."

Among the principles Obama laid out were:

n Challenging states to adopt world-class standards rather than a specific standard.

• Improving pre-kindergarten programs, including $5 billion in the stimulus plan to grow Head Start, expand child care access and do more for children with special needs.

• Reducing student dropout rates.

• Repeating his call for everyone to commit to at least one year or more of higher education or career training.

On charter schools, he said the caps instituted by some states on how many are allowed aren't "good for our children, our economy or our country."

The president acknowledged that a rethinking of the traditional American school day may not be welcome but is critical.