1.你最好把这本书放在你15岁儿子找不到的地方.
You’d better keep the book where your 15-year-old son can’t get his hands on it.
下面较好
You’d better keep the book away from where your 15-year-old son can get it
2. 成绩优秀的学生未必比他们得分较低的同学在学习上花费更多的时间.
High-achieving students do not necessarily put in more time on their studies than their lower-scoring classmates.
未必可以翻译为may not,而用not necessarily 欠妥,花时间用spend..on结构较好
3. 用功是重要的,但知道如何充分利用自己的才能更重要得多.
Working hard is important, but knowing how to make the most of one’s abilities counts for much more.
这句用词太过生硬,用learning比knowing好
Working hard is important, but leaning how to make the most use of your abilities counts more
4. 她要求学生独立思考,而不是告诉他们该思考什么.
She asked her students to think for themselves rather than telling them what to think
对不起,疏漏了点,应该用think by themselves (用for表示为自己着想)