Preschool can provide an important introduction to the notion of schooling. For many children, preschool provides a "head start" in learning certain academic skills that they will be expected to learn in kindergarten and first grade.
If your child has attended a good preschool program, he will already have some rudimentary knowledge of such concepts as colors, shapes, numbers, and letter recognition (as well as the sounds that different letters produce).
Although the introduction to academic skills can give preschoolers a head start on kindergarten learning, preschool can have an even more important role in preparing kids for school. If your child has been attending preschool, the experience has given him the opportunity to develop social skills in group situations.
When you were a child, concepts such as colors, shapes, numbers, and letter recognition were taught in kindergarten. They still are; but today with two-income families and single working parents, children are exposed to these introductory academics in preschool or daycare programs. So if your child hasn't been in a preschool program, he may find himself behind the other children unless you've taken the time to teach him these skills.
Day care or preschool also gave your child the opportunity to develop strong friendships. Preschool provided day-to-day (or every other day, depending on how often your child attended) contact with the same children. Hopefully, this regular contact has allowed certain friendships to build. And his ability to form friendships will go a long way toward making your child's kindergarten experience easier.
Does this mean that if your child hasn't attended a preschool program that he will be socially backward when he first enters kindergarten? Of course not. A child who has had little or no contact with other children his own age may have a more difficult time adjusting to kindergarten. But classes for preschoolers (in swimming, gymnastics, dance, crafts, and so on), library reading groups, informal play at local parks, and plenty of playdates—in other words, a preschool program that you've designed and supervised yourself—can offer similar opportunities to practice social skills both in groups and one-on-one.
So if you have made sure that your child has had opportunities to play and learn with other children his age, he will have had plenty of practice at getting along and cooperating with others. And if you've made sure that your preschooler had the opportunity to make close friendships by seeing one or two other children on a regular basis, then you can be confident that he will make friends in kindergarten.