He was definitely ready and had a wonderful first day with absolutely no tears or anxiety.
But the second day of school was a different story.
Nobody had explained to the child that if there was a first day there would also be a second day and many more to follow. When he discovered he needed to go back to school again and would have to keep on returning for years to come, he wasn't happy. He did manage the second and subsequent days without major problems, but perhaps it would have been easier if he had understood that the first day was only one of many.
In many areas the school year will be starting soon, so it might be a good idea to be sure any kids about to attend for the first time understand this is only the beginning of being a "big kid."