Will it be:
"Billy", said the teacher "is a fool." or
Billy said, "The teacher is a fool."
The meaning of this simple statement is completely changed by the way it is punctuated, hence the importance of knowing the correct punctuation. It is easy to teach kids correct punctuation as they first learn to write.
Bad habits are hard to break, especially if kids have not been taught the correct rules of punctuation. So, if you want to give your kid the edge, especially during later school years, t