As an adult, but also as a public school teacher, I completely understand why the concept of the viewings being held at the school just feels "wrong" to some. In my opinion, bringing a large number (likely the whole town) of freshly grieving family, friends and strangers into the school for a viewing of two recently murdered students is unsettling with a capital U. We owe our children uplifting environments, or, at the very least, a "neutral" place to learn and focus on academics and music and sports. Not the presence of hearses and coffins and not to mention, an uncaptured killer. Sorry to be blunt, but it's all just way too macabre.
IMO, small discussions/school meetings should be happening now in order to support and guide these overloaded, mixed up kids. Now, it's about circling the wagons for a bit, with a memorial a little down the road where the kids can choose to contribute with stories of the girls, music tributes, etc.