The tests we use to determine the grade are nationally norm-referenced tests. A student's performance is compared to the performance of other students from across the nation who took the same test. A student is ranked by using this data. The 50th percentile rank is the national average. Transportation is usually the parent's responsibility.
School districts make their own rules and deadlines for applications.
Some cut-off dates are as early as January for the next school year. Check with the school district for their procedures. Schools are not required to calculate this rate and there doesn't seem to be a standard formula for those that do. It usually means the percentage of students transferring in and out of the school during the school year.