... just ask Barack Obama who says he quit coaching his daughter's 4th-grade hoops team after too many parents whined that he gave Sasha's squad an unfair advantage!

Obama spells out the whole thing in his new memoir, "A Promised Land" -- saying around 2010, he realized Sasha's team needed some help and volunteered to take over as head coach along with his personal aide, Reggie Love.

FYI, Love played college basketball at Duke!!

"After observing an adorable but chaotic first couple of games, Reggie and I took it upon ourselves to draw up some plays and volunteered to conduct a few informal Sunday afternoon practice sessions with the team,” Obama says in the book.

Obama says ... during the workout sessions, he and Love drew up plays and worked on "dribbling, passing, making sure your shoelaces were tied" -- you know, the basics.

The good news ... Obama ended up coaching Sasha's squad (which included Joe Biden's granddaughter, Maisy) all the way to the championship game, which they won in an 18-to-16 "nail biter!"

"[We] celebrated like it was the NCAA finals," Obama says.

The bad news ... Obama says other parents from opposing teams complained, claiming their kids were at a distinct disadvantage because they didn't have the leader of the free world on their squad!!

At one point, Obama says Love joked about the opposing parents saying, "They must think being coached by you is something they can put on their Harvard application."

Obama eventually says the bitching became too much -- so he stepped away from the coaching gig and returned to running the country full-time.