All children develop the skills needed to begin reading at different rates. Some children demonstrate a love for books, sounds, letters, etc. very early on while other children can barely sit still through a simple picture book.
Although most children are not able to read at 3, for those children who develop an early love for reading, at age 3 they may be beginning to play with sounds, letters, and rhymes which are all pre-reading skills. Although a preschool is not likely going to be teaching reading at 3, they will begin to introduce the children to letters and sounds to help with these pre-reading skills.
If your child seems to be advancing at a faster rate than other children, talk to the preschool teacher about ways to help foster your child’s reading skills and his or her love of reading.