When my son was 3.5, I approached our public school to explore kindergarten entrance the following year, when DS would have been 4.5, and they literally laughed in my face. So I instead enrolled DS, a year early, in a small, flexible, private school that has been a perfect fit. The private kindergarten had less than 10 kids, so I knew DS wouldn't get lost in the crowd, and he was tall, mature and very social in addition to being ready academically.
In our case, getting that early start went a long way toward ensuring that the lower grades were challenging and enjoyable for DS. It also meant that when DS was later skipped from 4th to 5th, it felt and appeared like he'd only been skipped one grade, even though he was two years older than his classmates. So, my advice is, if you think your child will need to be skipped more than once, getting one "skip" in early can make for less disruption later on.
