Umm...IQ scores tend to be stable throughout life, and ability early in life is predictive of ability later in school. Kids who are slow in kindergarten, with few exceptions, do not go on to be whizzes in the 5th grade. Also, it's not like gifted programs are only limited to kindergartners.
Not just IQ: "A study from the University of Minnesota, recently published in Proceedings of the National Academy of Sciences (PNAS), found that conscientiousness — a family of personality traits that combines being disciplined, focused, tenacious, organized and responsible — is the personality trait that best predicts work-related success across the board in life. This includes everything from performing well at work, to managing work-life balance, to being successful in training and learning, and even leading a happier life."
