Definition
This phrase is used to indicate that someone has learned a lesson from experiencing the negative consequences of their actions, and will likely avoid repeating those actions in the future.
这下（某人）该知道（做某事的）后果了
She failed the exam because she didn't study properly; that'll teach her to prepare for exams better next time.
她因为没有好好准备而考试不及格；这下她学到教训了，下次会好好准备考试。
He was disqualified from the interview for being late; that'll teach him to be punctual for appointments.
他因为迟到而失去了面试资格；这下他学到教训了，以后会准时赴约。
They went hiking without checking the weather forecast and got completely soaked. That'll teach them to check the weather before going out.
他们没有查看天气预报就去爬山，结果全身湿透了。这下他们学到教训了，以后出门前会先看天气。