Background: Early and effective treatment for children with developmental language disorder (DLD) is important. Although a growing body of research shows the effects of interventions at the group level, clinicians observe large individual differences in language growth, and differences in outcomes across language domains. A systematic understanding of how child characteristics contribute to changes in language skills is still lacking. Aims: To assess changes in the language domains: expressive morphosyntax; receptive and expressive vocabulary; and comprehension, in children in special needs education for DLD. To explore if differences in language gains between children are related to child characteristics: language profile; severity of the disorder; being raised mono- or multilingually; and cognitive ability. Methods & Procedures: We extracted data from school records of 154 children (4-6 years old) in special needs education offering a language and communication-stimulating educational environment, including speech and language therapy. Changes in language were measured by comparing the scores on standardized language tests at the beginning and the end of a school year. Next, we related language change to language profile (receptive-expressive versus expressive-only disorders), severity (initial scores), growing up mono- and multilingually, and children's reported non-verbal IQ scores. Outcomes & Results: Overall, the children showed significant improvements in expressive morphosyntax, expressive vocabulary and language comprehension. Baseline scores and gains were lowest for expressive morphosyntax. Differences in language gains between children with receptive-expressive disorders and expressive-only disorders were not significant. There was more improvement in children with lower initial scores. There were no differences between mono- and multilingual children, except for expressive vocabulary. There was no evidence of a relation between non-verbal IQ scores and language growth. Conclusions & Implications: Children with DLD in special needs education showed gains in language performance during one school year. There was, however, little change in morphosyntactic scores, which supports previous studies concluding that poor morphosyntax is a persistent characteristic of DLD. Our results indicate that it is important to include all children with DLD in intervention: children with receptive-expressive and expressive disorders; mono- and multilingual children, and children with high, average and low non-verbal IQ scores. We did not find negative relations between these child factors and changes in language skills.