Recent ERP research with adults has shown that the online processing of subject-verb (S-V) agreement violations is mediated by the relative perceptual salience of the violation (Dube et al. 2016). These findings corroborate infant perception research, which has also shown that perceptual salience influences infants’ sensitivity to grammatical violations (Sundara, Demuth & Kuhl 2011). This raises the possibility that similar effects may manifest in school-aged children. To investigate this possibility, we recorded ERPs while 9–11-year-old English-speaking children (n = 24) listened to sentences with grammatical versus ungrammatical subject-verb agreement (i.e., third-person singular). Ungrammatical verbs differed in their relative perceptual salience due to the overtness of the error—errors of commission (i.e., superfluous -s) versus errors of omission (i.e., absent -s), and the position of the violation—utterance-medial versus utterance-final. Overall, the violations elicited an N400 effect, indicating that children were sensitive to the grammaticality differences. However, this effect was only significant for errors of commission, and utterance-position did not play a role. These results differ from those of adults, where both errors of omission and commission elicited a P600 effect, which was larger in utterance final position. These findings suggest that the relative perceptual salience of the grammatical violation influences the processing of S-V agreement in both children and adults, but the processing strategies differ, with children relying more on local, shallow processing rather than global, deep processing.