Presenting the past simple auxiliary to students

[greystroke]

Hi,

My students have a problem with the formation of the past simple auxiliary.( I think its to do with their mother tongue)

E.g. I didn't knew the answer
I didn't had my lunch.

I have presented ( Text based presentations, personal experience etc.) and practised the structure( Gap fills, substitution tables) many times with them , but they still make mistakes.
Is there any way I can help them correct their mistakes and practice the structure further?
I'd appreciate any help .

Arun

[Horsa]

The problem seems to be that they haven't understood that the auxiliary expresses the past and not the main verb. So why not try an error correction exercise. Give them twenty incorrect sentences. Elict why they are wrong and then get them to correct them while working in pairs.