It depends on the birthday

Most kids start kindergarten at five and go into first grade at six, but if they are born late in the year (usually mid-October on, depending on the school) and won't turn six until after the school year starts, they miss the cut off and can't start first grade until the following year, when they are about to turn seven. I hope I said that clearly. I have one son that was born mid-year and one that was born late, so I know this cut-off thing intimately.