How to Teach Sentence Structure: From Simple to Complex Without Losing Anyone

If sentence structure feels like the hardest thing to teach well, you're not wrong. It sits at the intersection of grammar, syntax, and rhetorical choice — and most curricula handle it badly, jumping from 'a sentence has a subject and a verb' to 'now write a complex sentence' with nothing in between.

This post walks through the actual sequence. Six stages, with the activities and sample sentences I've used to move secondary students — ELLs, struggling readers, and on-grade-level writers — from kernel sentences to controlled compound-complex constructions over a single semester.

Related reading: Sentence Structure Activities for the activity bank, and our Ultimate Guide to Teaching Grammar to ELL Students for the wider context.

Why Sentence Structure Is Worth Teaching

Two reasons. First, students' writing is judged on sentence variety. Every secondary writing rubric has it. Students who write only simple sentences max out at proficient; students who control complex and compound-complex sentences hit advanced.

Second, reading comprehension follows sentence-structure knowledge. Students who can't parse a complex sentence in writing struggle to parse one in reading. The 2018 IES Practice Guide on writing instruction explicitly links sentence-level writing instruction to reading comprehension gains.

Stage 1: Kernel Sentences

Start with the smallest possible sentence. Subject + verb. No modifiers. No objects.

Birds fly. Dogs bark. Students read.

Activity: Strip It Down. Give students a 12-word sentence. Their job is to cross out everything that isn't needed for it to be a grammatical sentence. They should end up with 2–3 words.

Why this matters: students who can identify the kernel can identify the kernel inside a 25-word complex sentence — which is exactly the skill that unlocks both reading and writing.

Stage 2: Expanding Kernel Sentences

Now we add. Adjectives, adverbs, prepositional phrases — one element at a time.

Birds fly.
Small birds fly.
Small birds fly south.
Small birds fly south in winter.

Activity: Build a Sentence. Give students a kernel and a word bank. Add one element per round. After 4 rounds, every student has a different but grammatical sentence.

This stage is undervalued. Most students rush past it. Don't. Spend at least a week here.

Stage 3: Compound Sentences

Two kernels joined by a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so).

Birds fly south. Squirrels gather nuts.
→ Birds fly south, and squirrels gather nuts.

Activity: Combine the Pair. Give students 10 sentence pairs. They join each pair using a FANBOYS conjunction. The correct comma placement (comma BEFORE the conjunction when joining two independent clauses) gets taught here, in context.

Common confusion: students will want to join with just a comma. That's the comma splice. Name it explicitly: 'A comma alone can't hold two complete thoughts together — it needs a FANBOYS or a period.'

Stage 4: Complex Sentences with Subordinating Conjunctions

This is where students' writing transforms. Complex sentences use subordinating conjunctions (AAAWWUBBIS: after, although, as, when, while, until, before, because, if, since) to attach a dependent clause to an independent clause.

I was tired. (simple)
I went to bed. (simple)
Because I was tired, I went to bed. (complex — comma after introductory dependent clause)
I went to bed because I was tired. (complex — no comma when dependent clause is at the end)

Activity: Front vs. Back. Give students 8 dependent clauses. They write each one twice — once at the beginning of a sentence, once at the end. They notice the comma rule themselves.

Pro tip: post AAAWWUBBIS on the wall. Reference it daily. It becomes the secret weapon for academic writing.

Stage 5: Compound-Complex Sentences

Two or more independent clauses + at least one dependent clause. This is the pinnacle of academic sentence structure.

Although I was tired, I went to the store, and I bought milk for breakfast.

Activity: Sentence Surgery. Give students a compound-complex sentence. They underline the independent clauses, circle the dependent clause, and label the conjunctions.

Then they write one of their own. By stage 5, most students can do this with scaffolding; mastery comes from repeated production, not from explanation.

Stage 6: Sentence Variety in Real Writing

The final stage isn't a new structure — it's deploying structures intentionally in real writing. The benchmark: a paragraph with at least one of each (simple, compound, complex) and ideally one compound-complex.

Activity: Variety Audit. Students color-code their own draft: yellow for simple, blue for compound, green for complex, purple for compound-complex. They count. If 80% of their sentences are simple, they revise to add variety.

This activity makes sentence variety visible. Students can see what they're producing and what they're missing.

Sentence Combining: The Most Evidence-Backed Activity

If you only have time for one sentence-structure activity, make it sentence combining. The research base is enormous:

• Hillocks (1986) meta-analysis: sentence combining produced larger writing gains than any other grammar instructional approach.
• Saddler and Graham (2005, Journal of Educational Psychology): explicit sentence combining instruction significantly improved sentence quality in struggling middle school writers.
• Andrews et al. (2006) systematic review for the EPPI-Centre confirmed sentence combining as one of the few grammar interventions with strong evidence for transfer to writing.

The mechanism is straightforward: students learn syntactic patterns by producing them under cognitive demand, not by labeling parts of speech.

A 5-Minute Sentence Combining Routine

Run this 3x per week:

Given:
- The student was nervous.
- The student gave the speech.
- The speech was about climate change.

Possible combinations:
- The nervous student gave a speech about climate change.
- Although nervous, the student gave a speech about climate change.
- The student, who was nervous, gave a speech about climate change.

Notice: multiple correct answers. That's the point. Sentence combining is a generative exercise, not a single-answer one.

Common Mistakes Teachers Make

Mistake 1: Teaching the labels before the patterns. Knowing that a sentence is 'complex' doesn't help you write a complex one. Teach the pattern; the label can come later.

Mistake 2: Skipping Stage 2. Expanding kernel sentences feels too easy, so teachers skip to compound sentences. But sentence expansion is what builds the modifier flexibility that distinguishes mature writing.

Mistake 3: Drilling FANBOYS and AAAWWUBBIS without writing. Students can chant the lists and still not use them in their writing. Always anchor lists to production.

Mistake 4: Correcting comma errors without re-teaching the rule. When a student comma-splices, don't just add a period — return to the structural rule. The error reveals the misunderstanding.

Sentence Structure for ELLs Specifically

ELLs benefit from:

• Sentence frames (Although ___, ___) before they generate their own.
• Bilingual examples for languages that build sentences differently (German end-verb, Japanese SOV order).
• Lots of oral sentence combining before written. Saying the combined sentence aloud loads it into working memory.
• Color-coding subjects and verbs in mentor sentences before asking students to produce.

See Sentence Structure Activities for an ELL-friendly activity bank.

Frequently Asked Questions

How long should this sequence take? A semester for full mastery. The six stages run over ~16 weeks if you spend ~2 weeks per stage with continuous spiral review through bell ringers.

Do I need to use the terms 'independent clause' and 'dependent clause'? Yes, eventually. Start with 'complete thought' for newcomers, then introduce the terms by Stage 4. Students need the metalanguage to talk about their own writing.

What about students who already write complex sentences? Push them to compound-complex with deliberate stylistic moves: dashes for emphasis, semicolons for parallel ideas, absolute phrases. Sentence variety is a ceiling-less skill.

Does sentence-combining work for ELLs at all proficiency levels? Yes, but the kernel sentences need to be at their proficiency level. Beginning ELLs combine 2-word kernels; advanced students combine 5-word kernels with modifiers.

How do I assess sentence structure? Count clauses per sentence in a 250-word writing sample. Average should grow from ~1.2 (mostly simple) at Stage 1 to ~1.8 (mix of simple, compound, complex) by Stage 6.

Where to Go Next

Three concrete next steps:

1. Run a baseline. Have students write a 5-sentence paragraph. Count clauses per sentence. Note the average.
2. Pick one stage to focus on for the next 2 weeks based on what your students need most.
3. Automate the practice. Grammar Spy Membership sequences sentence-structure missions in this exact order, generates the combining activities, and tracks clauses-per-sentence growth automatically.

Sentence structure is teachable. It's just rarely taught in this sequence. Run the stages, do the combining, and watch student writing transform.