Does the expression 'quiet like a Sunday morning' have a Christian connotation?

I was reading an excerpt from the book 'The Last Lesson' by the French novelist Alphonse Daudet for my class when I came across the expression 'as quiet as Sunday morning'.

My first guess was that the expression is implying that Sunday mornings are quiet because it's a holiday and everyone is at home, possibly sleeping.

But can the expression also mean that everyone is in the church for the church service (I'm from India, so I know very little about Christianity).

Here's the expression it's proper context -

Usually, when school began, there was a great bustle, which could be heard out in the street, the opening and closing of desks, lessons repeated in unison...But now it was all so still! I had counted on the commotion to get to my desk without being seen; but, of course, that day everything had to be as quiet as Sunday morning.

In Daudet's time churchgoing was a social norm, also all shops were closed on Sundays and children were expected to play quietly. So Sunday mornings would have been quiet for both religious and social reasons. Also, of course there were no classes, so a school would be silent!

The phrase 'Sunday morning' indeed highlights the contrast in the school atmosphere that day with the other days. The usual commotion was nowhere to be seen, instead was replaced by the pin drop silence which prevailed in the 1870s for both religious and social reasons on 'Sundays'.