請依下文回答第 21 題至第 25 題      Recently economists looked at the relationship between pupils’ month of birth and their schoolperformance. It was found that among fourth graders, the oldest children scored on math and readingsomewhere between four and twelve percentile points better than the youngest children. That can beexplained as a “huge effect.” It means that if you take two intellectually    21      fourth graders with birthdaysat opposite ends of the cutoff date, the older student could score in the eightieth percentile,    22    theyounger one could score in the sixty-eighth percentile. That’s the difference between    23    for a giftedprogram or not. The economists said, “We do ability grouping early on in childhood. We have advancedreading groups and advanced math groups. So, early on, if we look at young kids, in kindergarten and firstgrade, the teachers are    24    maturity with ability. And they put the old kids in the advanced stream,where they learn better skills; and the next year, because they are in the higher groups, they do even better;and in the next year, the same thing happens, and they do even better again. The only country we don’tsee this going on is Denmark.” Denmark waits to make selection decisions until maturity differences byage have      25   . This is because they have a national policy where they have no ability grouping untilthe age of ten.
【題組】21
(A) different
(B) equivalent
(C) redundant
(D) efficient