The kindergarten entry date for Florida is September 1st. A child must be 5 on or before September 1st to start kindergarten. So, if your son was born on or before September 1, 2006 then he can start kindergarten this year. Sounds like your son was born in January, 2007 then he'll start kindergarten next year.
Below is a list of the kindergarten entry date for Florida and other states for your reference.