I have two conjectures: one for primary-grade texts; and the other for non-primary materials. The conjectures are based on the wish that the number of words should suffice to evaluate grade levels.
Let W3, W4 and W5 be the number of words in 3, 4 and 5 sentences respectively. Then, the grade levels can be easily calculated:
* Primary Grade Level (PGL) = W3/10 to W4/10
* Higher Grade Level (HGL) = W4/10 to W5/10
Let us test these conjectures.
‘Just A Few Words, Mr. Lincoln’ by Jean Fritz is the story about the Gettysburg Address written for grades 2-3. Here are the opening sentences:
“President Lincoln was one busy man.
“He had two big jobs.
“He had to free the slaves.
“And he had to win the war. The Civil War.”
The Strain Index = 2.1 (S3/10, where S3 is the number of syllables in three sentences). And the PGL = 1.7 (W3/10) to 2.4 (W4/10).
The last page of the book contains the full text of Lincoln’s Gettysburg Address. Here follow the first and second paragraphs:
“Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.
“Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure. We are met on a great battlefield of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.”
Certainly, this is a non-primary-grade speech. The Strain Index = 9.5. And the HGL = 9.1 (W4/10) to 10.2 (W5/10).
We have successfully tested two samples: one for each conjecture. A single swallow does not make a summer, but surely is a sign of hope.