上句见：Day384
The Story of Philosophy《哲学的故事》第1章Plato第7节VI. The Psychological Solution第10段第2句：

For we are likely to have trouble with these children of ours if we undertake to explain and justify everything to their simple minds. We shall have an especially hard time when they arrive at the age of twenty, and face the first scrutiny and test of what they have learned in all their years of equal education. Then will come a ruthless weeding out; the Great Elimination, we might cal lit. That test will be no mere academic examination; it will be practical as well as theoretical: "there shall also be toils and pains and conflicts prescribed for them"(413). Every kind of ability will have chance to show itself, and every sort of stupidity will be hunted out into the light. Those who fail will be assigned to the economic work of the nation; they will be business men, and clerks, and factory workers, and farmers. The test will be impartial and impersonal; whether one is to be a farmer or a philosopher will be determined not by monopolized opportunity or nepotic favoritism; the selection will be more democratic than democracy.
浙江大学译本：当他们迈入二十岁，他们所受的平等教育第一次面临审视和考核之时，我们将遭遇一个极大的难关。

解析

1、We shall have an especially hard time when they arrive at the age of twenty, and face the first scrutiny and test of what they have learned in all their years of equal education.
迈入20岁，多年平等教育后他们将面临第一个全面考核时，我们就遭遇严峻挑战。
scrutiny: the act of carefully examining something especially in a critical way详细的检查；仔细的观察
But surprisingly, until now, no living stump has been subjected to detailed scientific scrutiny.然而令人惊讶的是，直到现在尚未有对活着的树桩进行详细的科学检查。《经济学人》

柏拉图教育也是要选拔的，20岁时要面临第一次大考，有甄选性的。中国学生第一次大考是15岁左右，有些国家则11岁分流。看来20岁还是比较晚的，柏拉图还是相当有耐心的，特别是在当时寿命。