440.numerous studies have been done on 
441.the mission of educating the young to be useful to society and to avoid wrongdoing can be fulfilled in many ways.
442.should learn more about the inner world of youngsters, try to understand them, and guide them to acquire a sense of self-worth.
443.whether sth is the best measure for handing any problem caused by children is up to the parents to decide—not the schools.
444.malnutrition
445.disturb the natural balance
446.a powerful corrective
447.don’t forget to flush. 便后要冲水
448.dyed yellow hair
449.it is not absolute that an intelligent couple will have a clever child.
450.a more environmentally friendly place to live
451.the dangerous gas given off by exhausts of cars , bus and lorries
452.plain looking face 平凡的长相