How to train lightweight Small Language Models using teacher–student learning.
🚀 Introduction — Why Distillation Still Matters
Even in 2025, when quantization and fine-tuning dominate the headlines, distillation remains the single most powerful way to transfer intelligence from a big model to a small one.
It’s the foundation behind models like:
- Phi-3 Mini (distilled from GPT-4-level instruction data)
- TinyLlama (distilled from LLaMA-2 7B)
- Gemma 2B (refined from PaLM and Gemini data pipelines)
Distillation lets developers train faster, deploy smaller, and retain quality — all while staying within hardware limits.
🧠 Step 1: What Is Knowledge Distillation?
Knowledge distillation trains a smaller “student” model to replicate the outputs of a larger “teacher” model.
The process focuses on soft targets — the probabilities or logits of the teacher’s predictions — rather than hard labels.
Simple Concept:
Teacher: Large model (e.g., GPT-3.5)
Student: Small model (e.g., TinyLlama 1.1B)
The student learns to match the teacher’s “thinking process,” not just the final answer.
It’s not imitation — it’s compression of intelligence.
⚙️ Step 2: The Two Types of Distillation
| Type | Description | Example |
|---|---|---|
| Logit Distillation | Student learns from the teacher’s probability distributions | Text classification |
| Response Distillation | Student mimics the teacher’s textual outputs | Instruction fine-tuning |
In modern SLM training, response distillation dominates — often via synthetic datasets generated by large models (GPT-4, Claude, Gemini).
🧩 Step 3: Building a Dataset
You’ll need pairs of (prompt, response) examples from the teacher model.
Example Python script:
import openai, json
prompts = [
"Explain the concept of gradient descent simply.",
"What are the benefits of model quantization?"
]
data = []
for prompt in prompts:
completion = openai.ChatCompletion.create(
model="gpt-4",
messages=[{"role": "user", "content": prompt}]
)
data.append({"prompt": prompt, "response": completion["choices"][0]["message"]["content"]})
json.dump(data, open("teacher_responses.json", "w"))
✅ Result: Your synthetic “teacher” dataset — ready for student training.
⚡ Step 4: Fine-Tuning the Student
You can fine-tune a smaller model (e.g., TinyLlama or Phi-3 Mini) on the teacher-generated data.
from transformers import AutoModelForCausalLM, AutoTokenizer, Trainer, TrainingArguments
model_name = "TinyLlama/TinyLlama-1.1B-Chat-v1.0"
tokenizer = AutoTokenizer.from_pretrained(model_name)
model = AutoModelForCausalLM.from_pretrained(model_name)
dataset = load_dataset("json", data_files="teacher_responses.json")
training_args = TrainingArguments(
output_dir="./distilled_tinyllama",
per_device_train_batch_size=2,
num_train_epochs=3,
fp16=True,
save_steps=200,
)
trainer = Trainer(model=model, args=training_args, train_dataset=dataset)
trainer.train()
✅ After 2–3 epochs, you’ll have a student model that captures much of the teacher’s reasoning — at a fraction of the compute cost.
⚙️ Step 5: Evaluation Loop
Use lm-eval-harness to benchmark the student:
lm_eval \
--model hf \
--model_args pretrained=./distilled_tinyllama \
--tasks lambada,hellaswag,gsm8k
Compare results with the teacher model to measure distillation efficiency.
🧮 Step 6: Key Metrics
| Metric | Description | Goal |
|---|---|---|
| Accuracy | How well the student replicates outputs | >85% of teacher |
| Perplexity (PPL) | Predictive fluency | ≤ 20 |
| Compression Ratio | Student size ÷ teacher size | ≤ 0.25 |
| Latency Gain | Speedup vs. teacher | ≥ 2× |
Example:
| Model | Accuracy | Size | Speed |
|---|---|---|---|
| GPT-3.5 (teacher) | 100% | 175B | 1× |
| TinyLlama 1.1B (student) | 89% | 1.1B | 12× faster |
🧠 Step 7: Advanced Techniques
- Progressive Distillation — Multiple teacher layers train intermediate student checkpoints.
- Self-Distillation — A model teaches itself iteratively (used in Phi-3 pipeline).
- Data Weighting — Weight samples by teacher confidence for stable training.
- Mixture-of-Teachers — Combine responses from GPT-4 + Claude for diverse generalization.
Modern pipelines often combine these for the best balance of accuracy and size.
⚡ Step 8: Real-World Pipelines
| Model | Teacher | Student | Framework |
|---|---|---|---|
| Phi-3 Mini | GPT-4 | 3.8B | DeepSpeed |
| TinyLlama | LLaMA-2 7B | 1.1B | PEFT |
| Gemma 2B | Gemini | 2.0B | TensorFlow |
| Qwen1.5 1.8B | Qwen-7B | 1.8B | Megatron |
All use synthetic response distillation — now the dominant trend in SLM production.
🧱 Step 9: Tools to Streamline Distillation
| Tool | Role |
|---|---|
| Hugging Face PEFT | LoRA / QLoRA fine-tuning |
| DeepSpeed ZeRO | Memory-efficient distributed training |
| Weights & Biases | Experiment tracking |
| lm-eval-harness | Post-training benchmarking |
You can build a full open-source distillation stack with these tools — no proprietary APIs required.
🔮 Step 10: The Future — Self-Distilling Ecosystems
The next wave of SLMs will distill themselves continuously via:
- Automated teacher rotation (use strongest models for hardest data)
- Self-feedback loops (reinforcement through evaluator models)
- Dataset refinement via reward modeling
Distillation isn’t just a training trick anymore — it’s becoming a learning philosophy.
Follow NanoLanguageModels.com for hands-on engineering guides to build, train, and optimize your own small models — from distillation to deployment. ⚙️