Sentence:  We speculate that compulsives in the unstructured schools <WSD>are</WSD> under greater strain because of the lack of systemization in their school setting , but that their need to organize ( for comfort ) is so intense that they struggle to induce the phonic rules and achieve in spite of the lack of direction from the environment . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)