Going Through the Gate — Janet S. Anderson

Every year, at the last one-room schoolhouse in the county, there is a special graduation ceremony for the sixth-graders. Everyone in town has gone through it, and no one is allowed to discuss it. Becky and her four classmates have been preparing for months, with help from their teacher, the mysterious Miss Clough. They've each chosen an animal to study, and they've learned it by heart -- in fact, they know so much that they could practically become their animals. And now it's the morning of graduation. It is time.