My son was given a number of sentences and was asked to underline the nouns in each sentence.
One of the sentences is:
The house is made of bricks.
In this case, should he underline "bricks" as a noun or should he not underline it because "bricks" was preceded by the term "made of" thereby making the phrase "made of bricks" an adjective?
Yes, he should underline "bricks" as a noun. The crucial point is that "made of bricks" is not an adjective; it's an adjective phrase that happens to contain the noun "bricks" (and the preposition "of"). "Bricks" is a noun functioning as object complement of the preposition "of"; it is not an adjective.
The individual words in a phrase are analysed according to their basic word category (part of speech). For example, the word "boys" is a noun, and when it occurs in an adverb phrase like "happily for the boys", it still retains its status as a noun; it doesn't suddenly become an adverb just because it's part of a larger expression that happens to be an adverb phrase.
So, whatever the phrase that "bricks" occurs in, it will always belong in the category 'noun'.