In a typical teaching sequence, the last sentence skills are long, compound-complex constructions and deliberate stylistic choices, built after subject and predicate, the four sentence types, and increasing length and complexity.
The storm, which had raged all night, finally passed, and the villagers came out. Compound-complex sentences are often saved for last.
Deliberate choices, such as placing a short sentence after a long one for emphasis, count as advanced style too.
The rain stopped, and we left, because the roads had cleared. Two joined parts plus an attached clause. This is the combination learners usually reach last, since it asks them to handle every simpler type at once. One secondary English teacher who shared her own sequence described spending at least a week on each sentence type, and about two weeks each on the complex and compound-complex types, treating them as the steps that need the most pacing time.
One secondary ELA teacher reports pacing that marks compound-complex sentences as the most demanding step on the ladder rather than a rare or optional one. She spends at least a week on each of the four sentence types, and the last two, complex and compound-complex, usually get about two weeks each.
The storm, which had raged all night, finally passed, and the villagers came out. A single sentence carrying a background clause, a main action, and a second action, the kind of load typical of a late-stage skill.
It helps to know what last means here. Last in this progression means the hardest stage to master in a slow climb, not a fixed grade or a permanently unreachable skill. Sentence complexity in writing keeps growing through the school years and even into young adulthood, so there is no single finish line.
A ten-year-old who can already write a compound-complex sentence has simply moved further along the ladder, while an adult learner can reach it at any age. If you struggle with it, you are not late or locked out, you are somewhere normal on a gradual progression.
: a skill coming last in the typical order does not make it rare or optional. It is late because earlier skills, like subject and predicate and the simpler sentence types, feed into it, and many learners are still building those first.