Children's pragmatic competence in deriving conversational implicatures (and scalar implicatures in particular) offers an intriguing standpoint to explore how developmental, methodological, and purely theoretical perspectives interact and feed each other. In this paper, we focus mainly on developmental and methodological issues, showing that children from age 6 on are adult-like in deriving the scalar implicature related to the scalar quantifier "some" (i.e. they interpret "some" as "some but not all"), while children at age 4 and 5 only sometimes reject underinformative-"some" in a classical Truth Value Judgment Task (Experiment 1). They do so despite their excellent performance in pragmatic tasks that evaluate their competence with the rules of talk exchange, such as the Conversational Violations Test (Experiment 4) and the Felicity Judgment Task (Experiment 5). To give children a better chance to reject underinformative-"some" when "all" is at stake, we manipulated the experimental design and materials in three different ways: 1) in Experiment 2, we tested the partitive "alcuni dei" ("some of") instead of the bare quantifier "qualche" ("some"); 2) in Experiment 3, we attempted to prime the scale [left angle bracket]some, all[right angle bracket] by asking children to judge a correct statement with "all" before the critical underinformative statement with "some"; 3) in Experiment 6, we aimed at making children more aware of the ambiguity of "some", between its basic meaning ("at least some, possibly all") and its strengthened meaning ("some but not all"). A surprising improvement is recorded in the last experiment, in which the rejection of underinformative-"some" by 5-year-old children rose to 72.5% (it was 42% in Experiment 1). We suggest that the children's low performance with scalar inference might be linked to the interplay of different factors as in the development of other general cognitive abilities, such as the ability to change one's strategy (Shallice, 1982) or to shift one's perspective (Gopnik & Rosati, 2001), the maturation of the lexicon (Barner & Bachrach, 2010), and especially their great sensitivity to the task, methodology and materials used to test their pragmatic abilities. (Contains 2 figures, 1 table, and 4 footnotes.)