Jessica Simpson's kids look like little models as they pose for school photos

Jessica Simpson's look-alike children are growing up so fast!

The proud mother shared a behind-the-scenes pic over the weekend of her 4-year-old daughter, Maxwell, and her 3-year-old son, Ace, flashing their biggest smiles while posing for school photos.

"Seriously?!?!?" Simpson gushed. "Thank you God for these precious kiddos. #maxidrew #aceknute"

Earlier this year, Simpson told ET that she credits her kids for keeping her in shape. "I think being a mom is enough of a diet," she quipped. "You have to run around chasing your kids, but I do eat a lot of their corn dogs, so I have to get on the treadmill a lot to watch my TV shows."

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As for whether she and husband Eric Johnson have plans to expand their brood, the 36-year-old star told ET, "I don't think I could have another baby right now. It was a very, very big shock after having a baby and four months later knowing I was pregnant again, so I think that's not in our near future."

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She added, "But people have kids at 40 now, so you never know."

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