I went to Stephen Miller's high school

[VOX]

78. Last year, the L.A. Times interviewed 20 people who knew Miller at Santa Monica High School...

And not one individual said a single word on record that corroborates the OP’s statement. The Times also ran a story on Miller in 2017 with an emphasis on his high school years, and again, there’s not a shred of corroborating information.

https://www.lamag.com/citythinkblog/stephen-miller-samohi-oral-history/
Trump Advisor Stephen Miller Has Always Been This Way
From “virtual loner” to the White House: An oral history of Stephen Miller’s days at Santa Monica High
Los Angeles Times Magazine, 10/30/2018
By Laurie Winer
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Los Angeles Times article from 01/17/2017:
https://www.google.com/amp/s/www.latimes.com/politics/la-na-pol-trump-speechwriter-santamonica-20170117-story.html%3f_amp=true