FYI -- Wade took part in a 4-day course called "The Business of Entertainment, Media and Sports" ... which required him to live on campus, eat at the student dining hall and basically study his ass off for 4 straight days.
We're told Wade didn't coast through the course -- several Harvard faculty members tell us D-Wade was very impressive and had one hell of a work ethic.
Wade and his classmates were required to brush up on case studies on several high profile people and sports teams ... including Beyonce, Real Madrid and LeBron.
NFL superstar Brandon Marshall took the course last year ... and came back to speak to the 51 students in the class this year -- and today, he told "TMZ Hollywood Sports" what it takes to make the grade.
It's no joke ... Marshall says the course is super tough and super competitive ... but he also told us the #1 thing athletes should take away from the class.