See above. As you can see, I am not entirely clear on what you meant by "original purpose of the noun".I learned that in some cases, zero article nouns mean the original purpose of the noun (What do you mean by "the original purpose of the noun?). So in 1, can it have a general meaning of "There is treasure like getting peace from prayer in church" (I would never take that meaning from the word "treasure") where church is used as an original purpose (Again, what do you mean by "an original purpose"?)? 2 definitely means physical treasure in a physical church.
What about 3? Can you use "in school" for generalization of a noun like school? It doesn't (missing word?) an unspecified school(a school) or a specific school(the school), which all mean physical places.
1.There is treasure in church. This is unnatural.2.There is treasure in the church. This could mean "in the church as a global institution" or "in a specific church" (the building).
3. In school, our children, the dream of our future grow. "In school" is fine here. The way you have worded it means that you consider that "our children" are "the dream of our future". Is that what you meant?
Student or Learner