Languages express events in the world by means of transitive and intransitive constructions, whose properties differ according to language typology. Children witness how specific languages express transitivity by listening to linguistic input, which varies according to contextual variables (such as the age of the speaker and the addressee). In this study, we investigated word order, one feature that typically helps discriminate between transitive and intransitive constructions but is more reliable in some languages than others. The frequency and consistency of word order as a cue towards clause transitivity was analysed in the input to 19 monolingual Spanish-learning children from Argentina (20 months old on average, SD=0.3), diverse in terms of socioeconomic status (SES). We found that some word orders occur far more frequently and/or indicate clause transitivity much more reliably than others. In addition, their consistency as transitivity cues varied across the registers and was crucially affected by SES.