By the time kids are 18, you're seeing a lot of these differences in teenage pregnancy rates and college attendance rates.

到孩子 18 岁时，您会发现少女怀孕率和大学入学率存在很多差异。

Researchers assessed academic performance using standardized test scores, as well as attendance rates, teacher-student ratios, and retention rates - which is the number of students required to repeat a certain grade.

研究人员使用标准化考试分数、出勤率、师生比和留级率来评估学习成绩—在某一个年级里，学生人数需要重复多次研究。