Carol,
My sister is working in a kindergarten, she suggests to give our BB to nursery at 2.5 yrs since she observed that BB at 2 yrs is a little bit small and may cried for a more long time and also all the BB must get sick when they go to school in the frist few month.
But as I said, our BB are small B so we can't give them to study at 2.5 age (since in May), just 2 months and then have a summer holidays and they may need to take another period to accomodate another school.