Every second language (L2) speaker will make grammatical errors, irrespective of age, education, motivation or learning context. Errors often persist even after focused teaching of the relevant forms and rules and abundant exposure to input through immersion. Errors may persist even in the language of young learners immersed in mainstream education. It is important to recognise that grammatical errors do not, in any way, reflect the cognitive abilities or intelligence of these young learners. Grammatical errors arise because learners have difficulty processing L2 forms which do not have easily identifiable meaning. Learning activities helping learners to process the relevant forms correctly can improve their accuracy. Such grammar processing activities need to take into account the degree of similarity between the target L2 forms and the first language(s) of the learners. Young immigrant children acquiring the language of their host country through immersion in mainstream education require support in their L2. Online grammar activities incorporated in a blended learning environment can provide a personalised approach, without disrupting children’s attendance in the mainstream classroom.