WASHINGTON -- Many states are facing an uphill battle when it comes to meeting goals set by the No Child Left Behind law, which could mean pink slips for teachers and headaches for parents.

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The federal law states that by the 2013-14 school year all students must pass state tests in math and reading.

About half of the states have steady annual goals for increasing the percentage of students passing, or working at their proper grade level. But according to a report by the nonpartisan Center on Education Policy, 23 states set the bar very low early on, so now expect big annual achievement gains in what the Center calls a "backloaded" approach.

The Center said it's unlikely that states taking that approach can make the kind of gains expected.

Educators said the strategy is like a balloon mortgage payment, in which home owners have a final payment that's much larger than previous ones.

"Many states may have originally set lower achievement goals for the first few years under NCLB in hopes of getting systems into place or gaining some flexibility from Washington later on," said Jack Jennings, president and CEO of CEP. "But right now, they are still on the hook for the academic equivalent of a mortgage payment that is about to balloon far beyond their current ability to pay."

The Education Department said nearly 11,000 schools, or a little more than 10 percent of all public schools, have missed their state-set progress goals and are taking corrective steps.

Schools that don't hit testing benchmarks for two years or longer face increasingly stiff consequences -- such as having to transport children to higher-performing schools or paying for tutoring to replace terminated staff thought to be a part of the school's problems.

Jennings said it's nearly impossible for many of the backloaded schools to make the drastic improvements.

"This problem cannot be solved by states alone. Congressional leaders must provide some assistance in the reauthorization of the law to help create a more reasonable and workable solution," said Jennings.