I have never known the level for our kids. They have been able to read anything they came across since age 3 or so, and the school certainly never tested them to capacity during reading screenings. But I think they don't feel an urgent need to know a level on a kid who reads well, and neither do I.
Our school also does not focus on choosing books at the "proper" level, except that the librarian has a rule that if you have to stop to figure out words 5 times on a single page, then the book is too hard. Otherwise, I think they use the levels only for remediating reading difficulties, which seems appropriate to me.
DeeDee
