First grade children don't generally think logically. For example, many don't yet use "because" correctly. Some have trouble with words indicating location -"over," "under," "behind," and "in front of." Most first graders don't realize that, by changing the shape of a ball of clay by rolling it out, the amount of clay remains the same - it just LOOKS different. Many don't see that, while two and three are five, by taking away the two and the three we are back at the starting point.
Once, when I was in the school office, all the lights went out. In a couple of minutes a first grade girl rushed into the office. She blurted out, "All I did was flush the toilet!"
We adults can mistakenly assume that first graders are capable of our ways of thought.
First grade children vary in their development. In first grade, boys, particularly, need time. It is a teacher's task not to worry. Often, a little bit of learning in a child is OK.
In a stimulating environment, all children grow in many ways.