Associated Press:

Results from national math and reading tests show slipping or stagnant scores for the nation's schoolkids.

Math scores were down for fourth and eighth graders over the last two years. And reading grades were not much better: flat for fourth graders and lower for eighth graders, according to 2015 results released Wednesday for the National Assessment of Educational Progress (NAEP) exam.

The falling mathematics scores for fourth and eighth graders mark the first declines in math since 1990.

The results suggest students have a ways to go to demonstrate a solid grasp or mastery in reading and math.

Only about a third of the nation's eighth-graders were at proficient or above in math and reading. Among fourth graders, the results were slightly better in reading and in math, about two in five scored proficient or above.

The report also found a continuing achievement gap between white and black students.

There were a few bright spots: the District of Columbia and Mississippi both saw substantial reading and math gains.

Education Secretary Arne Duncan urged parents, teachers, and others not to panic about the scores as states embrace higher academic standards, such as Common Core.

"We should expect scores in this period to bounce around some, and I think that 'implementation dip' is part of what we're seeing here," Duncan said in a phone call with reporters. "I would caution everyone to be careful about drawing conclusions."