Sometimes people use a noun modifier instead of an adjectival form of the same word. More often than not, there is no difference in meaning between the two but sometimes there is, such as The Education Bureau(which only tells us the Bureau is responsible for education) and an educational material(which otherwise tells us that the material is useful and helpful as far as education is concerned.
How to distinguish?
When a noun modifier is used, it is usually used to avoid the evaluative, descriptive or emotional characterisitcs of the primary functions of an adjective. Therefore, a horror film vs a horrible film, and the construction site vs a constructive idea.
Sometimes this type of distinction between evaluative and non-evaluative can also be made bewteen two similar adjectives like the one you raise:
an economic policy means a policy for managing the economy, whereas an economical housewife means a housewife who is clever at using her money.
(not a teacher)
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