Average scores on the ACT exam held steady for the high school class of 2012 but the results show modest progress in the number of students who appear ready for college-level work in math and science. The scores, being released Wednesday, cover the first-ever class in which more than half of graduates nationally took the ACT. Traditionally the ACT has been a rival college entrance exam to the SAT, but it is now taken by almost all students in nine states, and by at least 60 percent of graduates in 26 states.