Writing for the actual reading level

Which is frequently well below what the course assumes.

Learner populations in vocational training include people with interrupted schooling, people reading in an additional language, and people whose work involves very little extended reading. Materials pitched above their level do not teach; they filter.

Readability measures are crude and useful as a floor. They will not tell you whether writing is good and they will reliably identify material that is too dense, and running them costs nothing.

The more informative test is to have somebody at the entry level read a page aloud and explain it. Where they stumble is where the writing fails, and it is usually a specific construction rather than a general level.

Layout does as much as language. Short paragraphs, headings that say what the section is about, examples set apart from explanation, and white space all reduce the effort required, and dense pages defeat readers who could handle the content.

Where language and literacy support is genuinely required, that is a separate provision rather than something the resource can carry, and pretending otherwise leaves both the resource and the learner unsupported.

The other readability factor that is entirely within the writer's control is consistency of terminology. Materials that use three words for the same thing, because different sections had different authors, impose a translation burden that compounds across a whole document.