Iowa students did well in a recent science test. Overall, it could give cause for worry. Seniors taking the National Assessment of Educational Progress exam scored three points lower than those who took it four years ago. The N-A-E-C test ranks those with a fair, average and superior mastery of the subject, and found a slight drop in the number of seniors who had both medium and high-level scores. Then again, younger students do pretty well. Iowa kids in the 4th grade tied with Maine, Montana, Massachusetts and North Dakota for the best science scores in the nation. About 46-thousand students in forty states took the test for the national survey.