The delayed acquisition of Spanish "ser" and "estar" is generally understood as rooted in the cognitive demands imposed by the integration of semantic-pragmatic and world-knowledge factors associated with their lexical meanings. Here we ask (1) what is the nature of this language world-knowledge integration? and (2) what is the developmental trajectory including its age distribution? We examine Spanish copula production and comprehension in 142 children (age range: 4-12 years) and 26 adults. Using two tasks, sentence-choice (comprehension) and cued-production (production), we test the hypothesis that "estar" use is constrained by an ability to construe an alternative to the copula predication; an ability that develops with life experience. We test "estar/ser" use in two contexts: alternative-supporting, favoring "estar" use; and alternative-neutral, neutral regarding "estar" use, and possibly favoring "ser" use. The results show that for comprehension, children do not reveal adult-level sensitivity to context, exhibiting instead over-selection of "estar" sentences. For production, all children over-produce the "estar" sentence, even after having just chosen the "ser" counterpart. However, in this task, the 10- to 12-year-olds do behave similarly to adults and differently from 4- to 6-year-olds, consistent with our hypothesis. Alternative construal requires exposure to entities and properties in a variety of situations; exposure that older children are more likely to exhibit. Collectively, these results (1) support the properties of "estar" use hypothesized to underlie the language-world-knowledge integration, and (2) delineate a potential developmental trajectory whereby mastery of the copula may not begin to manifest until 10-12 years of age, not because of any one linguistic factor but rather due to specific world-knowledge exposure constraints.