(1)Elementary school 1 = Elementary school 2 = Elementary school 3 = Elementary school 4 = Elementary school 5 = Elementary school 6 = 12 years old
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(2)1st year of middle school = 11th year of middle school = 10th year of birth
(3)9th grade = born in 2009
(4)1st year of high school = 2nd year of high school = 3rd year of high school = Born in 2006
…A person was born in 2017