短语讲解：

1. The report looked at schools preparing students for a number of trades, including health-care assistant, dental assistant, auto mechanic and cosmetologist.

look at 看; 审视; 评判
例句：They would look at paintings together.
他们将一起观赏油画。
a number of 一些; 许多的
例句：Monkeys are transmitters of a number of dangerous diseases.
猴子是许多危险疾病的传染媒介。

2. They found lower pay benefits and higher debt for people attending private, for-profit schools, compared to public colleges in all 50 U.S. states.

compare to 一些; 许多的
例句：Two significant constants have been found in a number of research studies.
若干研究已经发现了两个重要常量。

3. However, about 40 percent of for-profit students leave school before completing their certification programs, according to the report.

according to 根据，按照
例句：According to etiquette, you should stand up to meet a guest.
按照礼节你应该站起来接待客人。