Private schools (at all grades) end at around 3:30 PM. Public schools (Elementary) get over at 2:00 PM. And Public schools (high school and middle school) end at 3:30 PM, but don't get home until 4:15 to 4:30 due to bus drivers. So public is probably the longest. Both private and public start at 8:00 AM and end at 3:30 PM (except elementary, which start at 8:00 and end at 2:00), there are 5 school days in a year.
In terms of learning, private schools have longer days as they start at 8.00 AM and end at 3.30 in all grades. This is unlike in public school where they start at 8 AM and end at 2.00 PM for elementary school. On average, a school day is 8 hours long; however, this differs depending on the school choice. A school year has an average of 180 school days.