rewrite the sentence, adding the missing helping verb.

(in the paper is) That make a lot of children unhappy.

my son rewrite the sentence and he write That will make a lot of children unhappy.

I agree

That's make a lit of children unhappy

"That makes a lot of children unhappy."

To rewrite the sentence and add the missing helping verb, you can say: "In the paper, that will make a lot of children unhappy."