The Orange County Register reports that Corona del Mar High principal Kathy Scott sent parents an email about the NFL-style "prom draft" over the weekend.
The long-standing tradition is not affiliated with the school and has operated mostly in secrecy.
Male students draw draft picks in a lottery but can pay to improve their draft number so they can pick the date of their choice.
Students had been posting on Twitter about the draft for the June 7 prom, but the posts have been removed.
In the letter to parents, Scott said it's not okay for students to be judged or objectified.
If it happens again, she said prom and other student activities may be cancelled.
(The Associated Press contributed to this report)