Freckle's leveling system assigns students an approximate grade level at which they are reading. Our leveling system takes into account text complexity, including sentence structure, sentence length, word length, and vocabulary. This is just one way to measure reading level.
Reading levels are generally expressed in ranges by grade level. There is no one specific level a 3rd grade student should be at, for example, but rather a typical range in which they should fall. Every student has a range of text levels that would be appropriate for them to read. Freckle recommends the level at which each student should read an assigned article, aiming to provide students with text within this range.
If you use another leveling system like Guided Reading, Lexile, or the Developmental Reading Assessment (DRA), consider looking at Scholastic's leveling correlation chart.