We don't want our son to become bored and disruptive in kindergarten, so we're thinking of having him tested and skipped into the first grade. We can't imagine that there'd be anything he'd learn in kindergarten that won't be covered in his preschool curriculum. Socially, we think he'd adjust fine. Since he usually plays with his older cousins (six and seven years old), he's in the habit of socializing with older kids already. We hear so many differing opinions on skipping grades when the child is young. We would appreciate some professional advice.
While I am sure your little boy is indeed advanced, we need to remember that most preschoolers learn best in a rote manner. The preschool gifted child will take material learned by rote (the alphabet, for example) and apply it in other ways or use it creatively. What I am saying is that just because the students in this school appear to be taking in a great deal of data, we can not be certain that they are all truly comprehending it and using it in a gifted manner.
To determine your little boy's true academic potential, I would suggest you consider a formal educational assessment. For better accuracy in determining his IQ, it would be best to wait until either after the four-year-old preschool year, or at least until spring of the four-year-old preschool year. No school will permit skipping kindergarten without a full educational assessment. For early entrance or grade skipping, some states require an IQ score of at least 130 or up. By the way, in my home state, kindergarten is required before a child is promoted to the first grade. This law has been in effect here for about a decade. You should check on your state's early entrance policies.
It is important that your son has the advanced social skills that you mention. It is also essential to consider his fine and gross motor skills. First grade will include a lot of writing work, plus skills like using scissors and other art supplies, and organized games.
Research states that to enter a grade early, the child should be at a level of achievement where the program can challenge the student without making special provisions for the child's age or developmental level. You will most likely need to review all the school options available to you to choose the school that best fits your son. You are correct in guessing that the typical kindergarten class is likely to have a curriculum comparable to what your son is experiencing now. However, it may be that if the area preschools are advanced, the grade schools have adjusted and upgraded their kindergarten curriculum. Only your local research will give you that answer. Don't just speak to the school office on the phone. Ask to observe a classroom if possible, and perhaps speak to a PTA member whose child has already completed the kindergarten program.
There are obvious advantages to seeking a challenging program for a gifted child through grade-skipping. There are also disadvantages that I am sure many have already told you (his friends will date and drive before him, he will be smaller in size for sports, etc.). One disadvantage that I never see mentioned is that your child will leave your home one or more years sooner if he is grade-skipped. Sure, he might postpone college but that is not the norm. We only get to have our kids with us for so long and I hesitate to speed up that time without the most extenuating circumstances. Thanks for asking a very interesting question.