The Good Morning America star attended the teenager's school graduation, and shared a heartfelt tribute to him following his milestone moment.
Alongside a picture of Duff smartly dressed in a suit while collecting his award, she wrote: "One more—because I just can’t believe he’s a graduate.
VIDEO: GMA's Lara Spencer makes sad discovery at family home
"Thank you @brunswickschool for making Duff so happy; for giving him an incredible education, the greatest friends and memories that he will cherish forever, and showing him what it means to be a kind, caring, compassionate young man.
"He will miss you terribly and so will we. #classof2021 #brunswick."
Prior to this photo, Lara had shared another picture of herself with Duff outside their house, and wrote: "It was senior prom for this guy last night and today is graduation.
GMA's Lara Spencer couldn't believe that her son had already graduated
"It’s still a few hours away and already I am tearing up. I know many of you have been here, and there is such comfort in that.
"My mom reminded me of a great saying that goes something like 'Don’t be sad that it’s ending. Be happy that it happened'.
"I can’t remember the exact wording so pls share it if you know it; and I would love to hear any other comforting words that might come in handy as I celebrate this milestone with my first born today. #graduationday #classof2021."
Lara with son Duff outside their home on graduation day
Lara shares her two teenage children, Duff and Katharine, with her ex-husband David Haffenreffer. The star was married to her ex for 15 years before they divorced.
She is now happily married to Richard McVey, and her son even walked her down the aisle at their nuptials.
The TV star with her husband Richard McVey
As well as spending time with her family, Lara is also incredibly busy with work. Not only is she a presenter on GMA, she has her own TV show, Everything but the House, too.
The HGTV series sees Lara working with a team of appraisers to help homeowners declutter their homes and auction off items.
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