Whether Albert Einstein showed early brilliance as a child seems to be a matter of opinion. His own stories of his childhood point to a strong intellectual curiosity, but he was continually discounted by educational authorities such as headmasters, who tended to either expel or insult the young Einstein.
One of Einstein's headmasters said that Einstein had a dull future ahead of him, an unfortunate statement considering how much that young boy went on to accomplish as an adult scientist. At times he displayed signs of developmental delay, such as taking a long time to begin speaking, but he typically earned good grades in school, especially in subjects like math.
Einstein's parents were concerned that it took the young boy so long to speak, and they even consulted a doctor. In the end, Einstein's development turned out fine. He displayed an anti-authoritarian streak in his childhood, which may explain why authority figures such as a school headmaster found him unimpressive or difficult.