Joe Kennedy III Says Trump Would Fail Elizabeth Warren's Law Class

Donald Trump wouldn't stand a chance in Elizabeth Warren's Harvard Law School class ... so says Rep. Joe Kennedy III, who calls Liz the best teacher he's ever had.

We got Joe on Capitol Hill Thursday and asked about his first professor at Harvard Law back in the day, and he gives Warren an A+ when it comes to teaching.

Joe is effusive in his praise for Elizabeth, telling us why she was so great at explaining law and its impact in the real world. He says Warren's the same in the classroom as she is on the campaign trail -- she brings out the best in people.

But, there's one person Joe thinks even Elizabeth couldn't prop up ... Trump.

Joe's mum on his grades under Professor Warren, who he calls a tough grader, but he did graduate ... and ya gotta hear what Joe says about Trump's ability to handle one of Liz's classes.

BTW ... Kennedy is set to make a big announcement Saturday. Looks like he's making a run for the U.S. Senate ... just like his famous grandfather, Bobby, and great uncles, John and Ted.