When you enter a Grade, your search results will show listings in the school boundaries of public schools that have your indicated grade. Not all elementary schools are K-5; for example, some are K-3, and if you have a 4th grader, the K-3 school is not really an option for you.
Schools in your selected Location(s) will be ranked according to test scores for the GRADE you select. Test scores are segmented by grade for every school. Other sites show one overall school score, so if one lower grade has superior testing results compared to the higher grades, the overall school score does not move significantly. This is how SchoolSparrow provides an opportunity to possibly uncover schools that are improving from the bottom up, by ranking schools according to the grade you indicate. Testing starts in the 3rd grade, there is no data for K-2nd grade.