Emily Shapiro, I am a former preschool teacher turned independent admissions consultant. .
Preschool is for 3 and 4 year olds, and in some schools includes 2's as well. Pre-Kindergarten is for 4 year olds, so it overlaps with preschool (the 4's year of preschool is pre-K). Age cut-offs differ in depending on your location. So does flexibility about the official cut-off. In my area, which is New York City, there is very little flexibility about the cut-off dates for most programs. Outside the city, independent (private) programs with December 31st cut-offs will often consider a child with a January birthday, especially if the class already has a preponderance of children on the younger end, November and December birthdays. If your boys will turn 4 in January, you can definitely enroll them in the 3's class of a preschool. If you would prefer to enroll them in a 4's class (pre-K), look for one with a December 31st age cut-off, and ask whether they would consider your children. However, consider carefully whether you really want them to be the youngest in their class, now and probably throughout their schooling. It is generally better academically for children to be on the older side than the younger, especially boys, whose fine motor control on average develops later. Also, unless they are physically large for their age, younger boys often feel at a disadvantage in sports. Being younger (and probably less mature) can be a liability socially. Without knowing your children, I can't make that judgment. I would, however, suggest that you think about it carefully. Maybe ask the opinion of your pediatrician. If you have a friend or neighbor or family member who is an educator, who knows your boys, and whom you trust, it might be helpful to ask that person's opinion.