'understand the lesson' is correct and usable in written English.
You could use it in a sentence such as, "I want to make sure I understand the lesson before I begin the assignment."
A quiz uses emoticons of smiley and sad faces so teachers can instantly gauge which students understand the lesson and which need help.
Only as the years slip by does she understand the lesson that the past — her own ancient tragedy — has taught her.
Just to see the uses made of calligraphy by Shirazeh Houshiary, Rachid Koraichi and Shirin Neshat is to understand the lesson in variety put forward here.
"And David Cameron should understand the lesson of this week: that he should start governing in the national interest not crude party interest".
In order to get from one level to the next, you must understand the lesson being taught and prove it through writing your own code.
If they cannot pass the exams, I try to design different activities and if their answers are wrong, I let them make collages to help them understand the lesson.
"We now understand the lessons, but Republicans have blocked all new safety laws," he said.
Unfortunately, they don't understand the lessons of their own experience.
God knows, everybody here, no matter how old or how young, should understand the lessons.
He closed with a reminder that it would take some time to fully understand the lessons of the crisis.
At the same time, it would understand the lessons of another Conservative-led administration: the National Government of 1931-35.
