Sentence:  Incidentally, they became mindful of the meaning of thrift and waste and learned to practice an economy of material and operations which was not elicited in the play with the more <WSD>ready-made</WSD> educational material. 
Meaning of the word marked with <WSD> tags:  Preexisting or made previously and suitable for use without (further) preparation or modification; "comparable with regard to the amount of preparation required".