The most important understanding science students should acquire is arguably an understanding of science as a way of knowing, one central to science but not specific to it. Students' own engagement in scientific inquiry and argument can support this developing understanding but does not guarantee it. We report the results of urban adolescents' participation in an extended intervention engaging them in guided inquiry and argument in exploring a multivariable database. Delayed posttest assessments with new content confirmed progress in developing the rich multivariable causal reasoning essential to science. Accompanying this progress was progress in understanding scientific practice, shown in the way students approached reconciling contrasting scientific claims, displaying understanding of when contrasting causal claims conflict with one another and require resolution and when they do not because they work together in a multivariable causal system. Such understanding is a prerequisite to the critical scientific endeavor of resolving diverging claims. Students showed greater benefits in these respects when the intervention activities involved content personally relevant to them and spanned more than one topic.