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It appears tight-fitting pants worn by females are too much, whether in the yoga room, as Lululemon learned the hard way last month, or, now, in the classroom.

A California junior high school last week announced a re-enforcement of its dress code banning leggings for girls that can be a "distraction" in the classroom.

"Leggings have become popular among girls and many are sheer," Emily Dunnagan, principal of Kenilworth Junior High in Petaluma, Calif., told ABCNews.com. "When girls bend in leggings the threads spread and that's really when it becomes a problem."

READ MORE: Minn. Principal Urges Students Not to Wear Leggings

Dunnagan called an assembly of 450 girls, ages 12 to 14, in the 900-student school last Thursday to review the school's dress code policy, something done annually this time of year as the weather changes, she said.

This time, however, Dunnagan stressed to the female students that they are required to wear a "school-appropriate length bottom," i.e. shorts, a skirt or a dress, over leggings. The message surprised the students and caused an initial backlash as parents and students alike wondered what would be allowed.

"The students asked specific questions about specific outfits and the message got lost in trying to clarify, 'Is this okay, is that okay?'" Dunnagan said.

After a subsequent email and auto phone call home to all of the junior high's students, Dunnagan says administrators received only around seven calls and emails protesting the policy and have had just four in-school infractions since.

The four girls who violated the policy received the school's typical dress code punishment of being temporarily pulled out of class to be outfitted in a new outfit of either long gym shorts or a yellow "School is Cool" t-shirt, depending on the infraction, before going back to class.

"Our dress code is vague because as styles change the dress code needs to change," Dunnagan said of the school's current code which states that, "No undergarments are to be shown in public," and requires that, "bicycle shorts may be worn under another garment."

Dunnagan's actions at Kenilworth came the same week as Rockville High School in Rockville, Md., made headlines for punishing freshman student Laura Woche when her top, worn over leggings, did not reach her fingertips. In that case the school, whose dress code specifically bans leggings worn as pants, gave Woche the option of wearing an oversized sweater or leaving school for the day and Woche's mother opted to pull her daughter out of school for the week, according to local station WTOP.

Dunnagan says the policy at her school is designed to do just the opposite, to keep kids in class and engaged in learning.

"This was a whole staff decision of everyone just wanting to make the school a distraction-free zone and allow kids to be kids," she said. "Part of becoming a teenager is expressing your individuality but we need to do that in a distraction-free way."