Nothing is certain. It could be written by a teacher wishing to impersonate an ESL student.
But, in my well-informed opinion (I used to teach English in Mexico), the structure of the language in the letter suggests with an overwhelmingly high degree of certainty that the writer is not a native speaker of English. Such writers, at least initially, attempt a word-for-word translation from their native tongue.
To wit, note just one sentence.
"Is* about time to let** the gun owner*** to be**** more careful of their gun***."
* "Is" in the place of "It is." This is common to speakers of romance languages -- in Spanish, for example, one would correctly write, "Es mi patria." (This is my homeland). "Es" means "is," so the sentence would commonly be written by an English Language Learner as "Is my homeland."
** "Let" and "make" (force) are often confused, as are do/make/take.
*** Failure to pluralize -- another mark of a language learner.
**** Use of infinitive in the place of a cojugated verb, as Don Gwinn pointed out.
Pax, I shouted because of the pointless exercise of turning a single blissninny letter into a condemnation of public education. It was just silly.
There's plenty to condemn in the letter, but the poor writing is pretty flippin' clearly a language barrier issue, not a fault in the child's education.