They also estimated that national trends in pupil-teacher ratios for black and white students between 1971 and 1999 accounted for nearly all of the narrowing of the black-white test score gap over that period, as measured by the NAEP exam.
他們還估計，在1971年至1999年期間，黑人和白人學生的學生與教師比例的全國趨勢幾乎佔據了NAEP考試所測量的那個時期黑白測試分數差距的縮小範圍。