Up until recently, the states have set their own goals and their own content standards. Those who set lofty goals had to punish their underperforming schools with staffing changes and diversion of budgets to private corporations who would serve as restructuring consultants. Those that set easily attainable goals still had difficulty getting 100% of their students to score at grade-level proficiency.

We still don't have national standards, but something like 80% of states have agreed to a new set of standards called The Common Core. In terms of critical thinking skills and college preparation, the Common Core standards are better. However, states don't have much money to spend on training, and there will be new tests to design on low budgets and in a rush. We can expect a bumpy transition.

But, yes, there's nothing in NCLB about helping gifted or even proficient students to stretch and grow. All of the targets involve the same percentage of various categories of students (racial, socioeconomic, disabled, English Language Learners, etc.) scoring as grade-level Proficient in reading, math, and whatever else the state reckons it can afford to test. If one of those categories (e.g., disabled) misses the target percentage, the school has not made Adequate Yearly Progress (AYP).

On the other hand, if the school has less than 40 students in one of the categories, they don't have to worry about that category. I actually had a restructuring consultant ask me to try to keep the number of special needs students below 40 for that reason. Anyway, that's why it is much more difficult for middle and high schools to make AYP than it is for elementary schools. The larger schools have to qualify in more categories.