Every school that holds a prom sets rules for what students and their guests can wear. Most of the time those rules are short, sensible and easy to meet. Sometimes they are long, specific and strictly enforced. Either way, they decide whether you get through the door.
This page explains what prom dress codes usually cover, how schools enforce them, and how to find and read yours before you shop. If you are unsure how dressed up to be in the first place, our page on prom formality explains black tie and the rest. This page also covers the legal limits on what a school can require, because those have changed more than many people realize.
Why schools have prom dress codes
Prom is a school event, even when it is held at a hotel or banquet hall. The same expectations that apply in the building generally apply at the dance, and many schools say so directly. One Florida high school's prom paperwork, for example, states that the district's code of conduct is in effect at all times, including the rules on dress.
Schools also write prom-specific rules because formalwear raises questions everyday clothes do not. High slits, open backs and cut-outs are common in prom collections. A dress code sets the line before anyone arrives, so the conversation happens in a fitting room rather than at the entrance.
What prom dress codes usually cover
No two schools use exactly the same wording, but most codes address the same handful of things. Here is how three real codes handled them.
Slits
Almost every code limits how high a slit can go. Harvest Prep's guidelines allow slits no higher than two inches above the knee, including side and back slits. Boylan Catholic High School in Illinois set the limit at three inches from the knee in its 2017 booklet. Cooper City High School in Florida allowed slits up to mid-thigh for its 2022 prom. The same dress can pass at one school and fail at another.
Backs
Open backs are the second most common rule. Harvest Prep's guidelines ban backless and halter styles and say the back must come up to bra height. Cooper City's rules for guests ruled out completely backless dresses. Boylan said back and side cuts could not go below the navel.
Midriff and two-piece sets
Two-piece prom sets are popular, and codes treat them very differently. Cooper City required one-piece dresses that show no part of the midsection, front or sides. Harvest Prep allowed two-piece dresses as long as no stomach shows, noting that stitching the pieces together may be required.
Necklines
Many codes ask for a modest neckline without spelling out a measurement. Boylan asked for necklines cut in a modest way without showing cleavage. Harvest Prep banned low-cut dresses and required bras, with strapless styles allowed if they give proper support.
Length
Prom is usually a long-dress event, but short dresses are often allowed within limits. Harvest Prep set the minimum at two inches above the knee. Boylan said no shorter than mid-thigh.
Cut-outs and sheer panels
Some codes ban cut-outs outright. Harvest Prep does. Others do not mention them, which leaves the decision to whoever is at the door. Sheer panels are the same. If your dress has them and your code is silent, ask before you buy.
Suits and tuxedos
Rules for suits are usually short. Cooper City asked for a tuxedo or suit and said jackets could come off if someone got too warm, but nothing else. Boylan listed a tuxedo, a suit with a tie, or a sport coat and slacks with a tie.
Guests have to follow it too
If you bring a date from another school, your school's dress code applies to them as well. Harvest Prep's guidelines say a student can be dismissed or disciplined if their guest's outfit breaks the rules. Some schools have guests sign the same agreement students sign. Send your date a copy of the code early.
How schools enforce it
Enforcement ranges from a quick look at the door to a formal approval process weeks before the dance.
The most common consequence is simple. You do not get in. Boylan's booklet said students who did not comply would be denied admission with no refund. Cooper City's guest terms said admission was conditional on proper attire.
Some schools go further and require approval in advance. Harvest Prep has students present the complete outfit, including shoes and undergarments, to a dress approval team, and says approved outfits must be worn as photographed. Alterations made to pass have to be reviewed too.
A few codes also say that the same dress can look different on different people. Boylan's booklet stated this directly. That is frustrating, but it is worth knowing. It means a friend's dress passing last year is not a guarantee yours will.
Rules based on gender
Some schools have had rules that only girls may wear dresses and only boys may wear tuxedos. Courts and civil liberties groups have pushed back on those rules.
In a 2024 letter to schools, the ACLU pointed to a 2010 federal case in Mississippi in which, as the ACLU describes it, the court found a school violated a student's First Amendment rights by barring her from wearing a tuxedo and bringing a same-sex date to prom. The same letter argued that sex-based dress requirements violate federal law, including Title IX and the Equal Protection Clause, while noting that schools may still require formal attire for events.
In practice, schools can require formal dress. Under the ACLU's reading of federal law, they cannot require a particular kind of formal dress based on a student's sex. Policies and their enforcement still vary by district. If a rule affects you, ask the school for it in writing and ask who to talk to about it.
How to find and read your school's code
Start with the prom page on your school website, the student handbook, or the ticket packet. Many schools post the code as a PDF, sometimes with photos of what passes and what does not. If you cannot find it, ask the class advisor or the student council.
Read it with a specific dress in mind, and use our six at-home checks to test it. Check the slit, the back, the midriff, the neckline and the length against the exact wording. Note anything the code does not mention, then ask about it. Bring a printed copy when you shop. A good stylist at a local prom shop will check dresses against it with you, and many shops have seen local schools' codes before.
If a dress you love does not pass, it may still be fixable. A tailor can often close a slit, add a mesh panel to a cut-out or back, or join a two-piece set. Ask before you buy whether the change is possible and what it will cost.