posted by Liz .
There are never enough discipline on the playground: someone always is getting hurt. Subject verb agreement.
Yes, there is a problem with subject-verb agreement.
In the first clause, the subject is "discipline." What should the verb be?
This sentence above is one terrible example of English. There should be a semicolon after "playground" instead of a colon.
I hope you read a lot of books and newspapers, so that you won't have to learn proper English grammar entirely from books like this one.