When Sienna Long was accepted early to her dream school, the University of Miami, her mother, Melinda Long, began planning a surprise party to celebrate.

Not just any surprise party, though. In late January, the elder Ms. Long, 48, threw her 17-year-old daughter a “bed party,” a relatively new style of celebration that involves tricking out a college-bound senior’s bed with university merchandise, candy and just about anything else one can buy in a particular school’s colors.

She hung orange and green streamers from the ceiling and tacked a university-branded bikini on the wall above the headboard, alongside a university flag. She set up giant light-up letters — “UM” — bedside an inflatable palm tree and plenty of balloons. On the bed, she piled new sweatshirts, T-shirts, shorts and more swimwear, along with a pair of special edition Nike sneakers.

Altogether it cost about $2,000, she said.

Ms. Long’s posts about the party on TikTok have inspired strong reactions. While some parents have asked her for tips on how to throw their own collegiate fetes, others have voiced frustration with the lavish and costly trend.

“Some people are like, What are you, nuts, lady? You know, they’re not wrong,” Ms. Long said. “This is a $90,000 college, and it’s just a college acceptance. It’s not a wedding, it’s not a shower.” (She added that not everyone who throws a bed party needs to spend nearly as much as she did.)

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