The story comes from Wasach County, Utah's FOX13:

Female students at a Utah high school want to know why their yearbook photos were altered to show less skin without them knowing about it. The students who were surprised to find their photos altered attend Wasatch High School, and some of them said they also feel upset because it appears the decisions whether to alter the photos or not weren’t made consistently....And that’s what bothered the girls the most. It seemed like the school randomly picked which pictures to edit. In one case, two different girls were wearing nearly identical tops: one photo was altered to add sleeves and the other was not.

View evidence of one of the yearbook alterations above. The school is claiming it has a well-known, well-publicized dress code that apparently the female shoulder-barers violated. (If such a code exists, why weren't the offenders sent home from school?)

The under-discussed component of this story: Mormonism, which views a bare female shoulder as a sign of disrespect if not apostasy. If a woman is a good Mormon, she's wearing her garment, which invalidate the possibility of bare shoulders. (At the least her shoulders are covered by her garment, and good Mormons make sure their garment is also covered by clothes.)

As commenter Kristin writes at FOX13:

If this were a predominantly Muslim public school, would it be appropriate to photoshop in a burqua? If this were a predominantly Jewish public school, would it be appropriate to photoshop in yarmulkes for the boys? Since when does a public school get to dictate that all students must dress according to the dress code of the predominant religion?