Graduations in churches?

A federal judge in Connecticut ruled that some high schools couldn't hold their graduations at a local mega-church. Before ruling, the judge visited the church. Here's apparently what their graduations looked like.

On the other hand, in the Chicago suburbs several high schools also hold their graduations at a mega-church, but one that has few religious symbols.

How this will play out will be great court fodder. The judge's ruling seems to hinge on an unacceptable level of religious iconography of the place in CT, however what about in Chicago where it's much more austere? What's an okay level--is any level okay? For the sake of familiarity, what if instead of a church, it was a mosque? What are the wider consequences of a ruling either way? How disruptive could that be?

My off the cuff thought is that money is fungible, so either way the government is putting money into a thing that will end up enabling religion--they're offsetting costs somewhere else that would have limited them.

On the other hand, churches are ubiquitous and offer convenient spaces, as used for polling places for example. I was surprised at first when I found out the polling place for my neighborhood in Madison was at a church. However, the basement of a church is magnitudes more secular than the service room(?). Perhaps churches owe a favor for being tax free?