The word 'concord' refers to words which, grammatically, have to go together to be correct. There is a real problem with concord, particularly in certain parts of the country, and it is really about the ability of your child to spot what is done in formal writing rather than what is said in school or at home.
'We was' and 'I were' are bizarre juxtapositions that, when I lived in the south were not really heard of. I used to gloss over the exercises in the books as the children couldn't understand why it was in there - you might as well have told them not to say 'We caterpillar' or 'I plinth' for all the relevance it had. However, in the north-west I've been shocked by people genuinely thinking that 'we was' is the correct part of the verb to use.
So what might you get in an 11+ paper to do with concord? Almost anything. The grammar section of an English paper could put simple questions such as this:
Insert the right word in the sentence below:
The boys ____ very happy as they had just won their football match.
In teaching a child how to do this, you need to think very carefully about your own language use. If you are using English as a second language or are used to a colloquial dialect, make sure that your child knows what is accepted in the home or local area, and what is accepted formal English. In particular, look at the verb 'to be' and all of its forms.
|I||am / was / will be|
|He, she, it||is / was / will be|
|You, we, they||are / were / will be|
In general, the singular forms use 'was' and 'is' while the plural forms use 'are' and 'were'.
There are many more complex questions than the initial concord one. Try this: Insert the correct word in the sentence below:
The man, unlike the woman, (is / are) here tonight.
The idea here is to work out whether or not the SUBJECT of the sentence is singular or plural. If it is in the singular, the answer will be 'is', if it is plural, it will be 'are'.
The subject of a sentence carries out the action. It is usually the noun before the verb, but in the more tricky examples it is hidden a bit. Let's look at this particular sentence:
|The man||unlike the woman,||(is / are)||here tonight|
The subject of the sentence is 'the man', which is singular, so the answer must be in the singular too. It should be 'is'.
So why do we get confused? The problem is, people picture two subjects as a woman is mentioned as well, making the subject appear to be two people. It isn't - the punctuation is helping to point out that the extra bit of information is not adding to the subject, just giving us some extra information.