Negotiating comprehension

I just had to include this entire blogpost from Academomia (written by my cousin,) because it's a fantastic example of negotiating for meaning--for sense-making. I'm afraid that a language learner might not be as persistent as 3-year-old Charlie:

On our way to church this morning Ryan and I were talking about our university's quarterback situation in which we lost a bunch of games, our starting QB was injured and taken out of a game that was not supposed to be that big of a deal but that we were barely hanging onto, our second string QB was put in, and we scored like a thousand points inside one quarter.
Ryan made the giant mistake of saying "Poor starting quarterback, that's a tough deal."
Charlie piped up from the back seat. "Wha happened to him?"
"Uh, our quarterback got hurt playing football."
"Wha happened to him?"
"He fell down during a football game and got a booboo. Now he is all better but the coach has to decide which quarterback is going to play the rest of the season."
"Wha happened to him?"
"Our quarterback fell down and hurt his leg, Buddy. He's fine, but now there are two good quarterbacks and the coach has to decide who gets to play."
"Wha happened to him?"
"Charlie, why don't you tell me what I've told you so far?"
"I don't know."
...
...
Ahhh.
"Wha happened to him?"
Sigh. "Our quarterback fell during the football game and hurt his leg. His mommy wrapped him up in a quilt, gave him some milk, and let him watch TV. Now he feels better."
"Oh."
Later after we picked him up from Sunday School Charlie skipped down the hall saying "The football player fell down and got a booboo and now there are two quarterbacks and his mommy wrapped him up in a quilt and let him watch George and that was SO NICE of her and now he feels ALL BETTER!"

Now that is real sense-making related to the experience of a three-year-old--comprehensible input, as it were! How do we recognize when our students haven't been able to make sense of what we're saying? A high school student is much less likely to persist, so we may not discover the problem before a test, unless we do careful and constant formative assessments.