Well, my daughter has gone back to College in Germany at age 34. She is the only American in her program of International students from place like the Middle East, Japan, Portugal and the U.K. For example, despite graduating from a PRIVATE American High School with a tougher curriculum that the public schools here, she never took Calculus in High School. Her College Calculus class was designed to be a review of High School Calculus, and it sunk her. It was material she had never seen before, yet her classmates said it was an EASY review. She is the only American in a new program so it is something the College is going to have to consider when admitting American students in the future.
It is clear to her, our high schools are not anywhere as tough in math and science education as those in other nations. By a long shot.
She admits, she has also discovered the entire concept of someone "going back to school" is a little out of sync outside the U.S. She is more than a decade older than her classmates. And older than most of her Professors.