rigorous

The best performing middle schools place great emphasis on “future-focus”—on rigorous high-school curriculum.

And for which had every Individual been hanged, few I imagine would think that Justice had been rigorous.

They were, besides, made amenable to a most rigorous system of laws, the least infraction of which was punished with death.

These castes were kept apart by a rigorous series of religious taboos.

But it was difficult to state intelligibly the grounds of this belief to that man of rigorous logic, if of infinite charity.

The luxury of them was new to him, yet not unpleasing after many years of rigorous self-denial and poverty.