I am a first grade teacher. Determining a reading level is based on assessment but you can get a ballpark idea and here are some suggestions. Of course, this is all based on my experience and others may disagree. In a classroom setting teachers consider students to be on level for instruction if they are reading a book at around 90 to 95% accuracy with very little support. Of course, they also should be able to read it fluently enough to understand what the story is about (fluency kicks in once kids are beyond the very early reader stage, when they have many more sight words). End of first grade level would be early chapter books (around Level 2ish) like Frog and Toad or Henry and Mudge. End of second grade level would be transitional chapter books like Magic Tree House or Junie B. There are many much more detailed lists of leveled books out there and I'm sure there are links to them on this site, but I generally tell parents that 90 to 95% accuracy (with comfortable fluency and comprehension!) means that it's about your child's level.
