My DD started kindergarten this fall at 3.8 years. Like you, it wasn't something we considered until her preschool teacher recommended it.
It has been a somewhat bumpy road, though not for the reasons we expected. She has been happy throughout, and thrived socially and academically. The obstacles were other parents and at times, her k teachers. But those were obstacles for us, and not anything that she was aware of or impacted by. The only things that she has really struggled with is being frustrated on occasion because she doesn't like being "the littlest" (youngest). And sometimes P.E. is frustrating because she can't run as fast as the other kids, etc.
If your DD is already doing afternoons with the class she'd be with for K next year, it sounds like she is a good fit both socially and academically as well. Also, you know her better than anyone. Do you think she'll enjoy the more academic afternoon of K, or will she not be comfortable with the structure of it despite her capability? Is there anything specific you're concerned about in connection with this placement?
Finally, do you think your daughter is able to observe to some extent the different afternoon groupings? Could you talk to her about the options and ask which she would prefer?
