As others have said, it depends on the situation, whether it's going to help or just distract the children.
While I may rephrase when I repeat back with children, I'm unlikely to directly correct phrasing unless that's already been agreed.
I still remember in my first few years in the UK how some had great glee in correcting me, and it was very tiring and never really helped our communication.
I can’t agree that it’s dialect. It’s merely incorrect, uneducated English, and ought not to be acceptable in a classroom.
Yes, in a classroom, having a standard is really helpful -- but that standard has and does change over time, and those in control put how they communicate as the correct, educated, proper way and it's always someone else that's the incorrect, uneducated one.
Standard British English is based on a few dialects that were used among the well-to-do who had the resources to be part of the process. This process was only back in the mid-18th to early 19th century when there was a strong push to develop a standard, in part to distinguish those like them as 'the educated'. We can see during and before this time that spelling and grammar, even of very educated people and the texts used to educate, varied widely. They weren't uneducated, it was just normal to write as one speaks.
There are English dialects where auxiliary verbs are commonly dropped, with some being more acceptable than others. People saying 'The room needs cleaned' rather than 'The room needs to be cleaned' are unlikely to get caught in a SPAG check, but ones like 'I done' will be. That correct line is flexible, changing over time with which dialects are normalised in a particular area, and which ones get dismissed as uneducated.