What does this poem mean?

-There once was a pretty good student

Who sat in a pretty good class

And was taught by a pretty good teacher

Who always let pretty good pass.

He wasn鈥檛 terrific at reading,

He wasn鈥檛 a whiz-bang at math,

But for him, education was leading

Straight down a pretty good path.

He didn鈥檛 find school too exciting,

But he wanted to do pretty well,

And he did have some trouble with writing

Since nobody taught him to spell.

When doing arithmetic problems,

Pretty good was regarded as fine.

5+5 needn鈥檛 always add up to be 10;

A pretty good answer was 9.

The pretty good class that he sat in

Was part of a pretty good school,

And the student was not an exception:

On the contrary, he was the rule.

The pretty good school that he went to

Was there in a pretty good town,

And nobody there seemed to notice

He could not tell a verb from a noun.

The pretty good student in fact was

Part of a pretty good mob.

And the first time he knew what he lacked was

When he looked for a pretty good job.

It was then, when he sought a position,

He discovered that life could be tough,

And he soon had a sneaking suspicion

Pretty good might not be good enough.

The pretty good town in our story

Was part of a pretty good state

Which had pretty good aspirations

And prayed for a pretty good fate.

There once was a pretty good nation

Pretty proud of the greatness it had,

Which learned much too late,

If you want to be great,

Pretty good is, in fact, pretty bad.The poem is about the idea that 'pretty good' is not, in fact, 'good enough'. Pretty good might let you get by, but it does not equate to excellence or greatness. The student becomes indicative of the state of the nation: if (for example) America is populated by those who are merely 'pretty good' then it cannot with a straight face refer to itself as 'the greatest nation on Earth'. By accepting substandard work as 'pretty good' you torpedo people's desire to be excellent, since being 'pretty good' requires much less effort.That a society where everyone thinks and learns in the same way is in fact an unhealthy one. We need diversity to develop.