My youngest DD's teacher kept starting her testing well below where she was capable of reading. What this meant for her was that the small mistakes kept her reading level lower than where she was capable of reading and comprehending. i.e. She couldn't move from level 15 to 16 because of small mistakes. After I talked to the school's literacy teacher 3 weeks later and explained she was reading words like "marvelous marshmallow world" and "whipped cream winter wonderland", they retested her as reading at level 21. Ironically, it was the same small mistakes kept her from moving to level 22.