All of the calming proposals create an imposition. The whole point of traffic calming is to impede the flow of traffic so as to reduce its speed. Without effective alternatives, reducing the speed of this road reduces its capacity to get people from one part of town to another, and it appears that state road 108 is, in fact a major road. It provides access to a number of businesses including a Walmart supercenter, churches, four public schools and city hall.
The obvious alternative to driving is a public bus service, which also uses the road. It stops near the two schools hourly most times of day.
So to make the interaction of the road and the schools safer, the city could redesign the road and make traffic worse, more substantially redesign the whole transportation infrastructure, or add a pedestrian overpass. The latter is not an insignificant project, but it usually costs less than the examples you linked.
Pedestrian overpasses require those who cross to physically climb over traffic. Better than a wall, but let's acknowledge the cost of that. They're also enormous and expensive, whether you design them terribly or well.[1]
The calming proposals include: narrower lanes, a raised median, and a traffic light to explicitly priortize and protect pedestrians when crossing. What about those makes them an imposition?
[1] https://candysdirt.com/2016/04/28/fugly-pedestrian-bridge-ha... http://m.sfgate.com/bayarea/place/article/Footbridge-an-eleg...