Oooh, statistics..JK :p
Means: Start of school year is 7.5. You have to add all the numbers and divide by how many numbers there are (14 in this case.) and end of school year is 8.214.
Medians: Just find the middle number after listing the numbers from least to greatest. If there are 2 numbers in the middle, add them then divide by 2. Beginning of school year median is 7.5. End of school year median is 12.
Range: subtract lowest number from highest. Beginning of school year range is 5 and end of school year range is 4.
Sorry I took long and hope I helped :)