A parochial school in Illinois isn’t taking any chances that girls attending its prom will be dressed immodestly.

So Boylan Catholic High School in Rockford recently issued a “proper dress and dance policy” to the student body for its upcoming prom, with 20 of its 21 pages aimed at the girls’ clothing choices.

Among the key areas covered are dress length, necklines (no cleavage), and any slits that might find their way into the dresses (no higher than three inches above the knee).

What’s more, the policy also takes on the sensitive topic of body types, leading to charges of body shaming, according to EAGnews.org.

The policy also comes with a stern warning: “Guidelines will be strictly enforced. Students, including guests, not in compliance with Dress Code will not be admitted to the dance and refunds will not be issued. There will NOT be a loaner clothing option. Dresses and attire that reflect modesty are required.”

The rules for the boys are summed up in one sentence: “Young men are expected to wear formal evening attire that would include a tuxedo, suit with a tie, or sport coat and slacks with a tie.”

But rules for the girls are extensive.

“[Dress necklines] must be cut in a modest way without showing cleavage” and any cuts in the back or sides “must not be cut below the navel (below your elbow),” the booklet says.

Dresses must also be no shorter than mid-thigh, and slits “may be no higher than three inches from the knee.”

Just in case written descriptions don’t get the message across, the guide comes with pictures to illustrate the dress code.

What has drawn the most criticism, however, involves body types.

“Some girls may wear the same dress, but due to body types, one dress may be acceptable while the other is not,” the booklet says.

Body image experts say this line is body shaming plain and simple.

“Girls do not have a choice in how their bodies were made so more voluptuous bodies are going to have more cleavage and curves. Taller girls’ dresses will hit higher up on the leg than a shorter girl. It’s nature,” Robyn Goodman, an expert on body image, told a local newspaper, the Register Star.

“Telling one girl she has to restrict her body by only wearing certain fashions and telling another her body is fine for any fashion is sending a message about what is the ‘right’ body to have and what is the ‘wrong’ body,” she adds. “These messages are often damaging to girls. We are not allowed to discriminate in the U.S. based on race, disability, gender, age, etc. … So why are schools discriminating against girls based on their bodies?”

Amy Ott, president of the Roman Catholic school, said that she understands that students come in all shapes and sizes but that everyone must be held to the same standards.

“You have to try a dress on and see what it looks like on you, not how it looks on someone else. … It’s like shopping for any other kind of clothing in this day and age. You want to look your best and look appropriate.”

Ott added that the policy was drafted after several girls were forced to cover up during the homecoming dance last fall.