The use of textbooks as primary sources of information has increasingly given way to tools based on Large Language Models (LLMs), raising concerns about the reliability of generated answers. This study investigates how different adaptation strategies shape the behavior of small language models in educational Question Answering (QA) tasks in Portuguese. To support this analysis, we built a question-answer dataset derived from an NLP textbook and compared base models and the Retrieval-Augmented Generation (RAG) pipeline with models adapted through supervised fine-tuning and Continued Pretraining. The evaluation relies on questions from the LARI dataset, which has been validated by human specialists, and combines automatic and qualitative assessment procedures. The findings indicate that small models tuned with structured instructional knowledge achieve stronger semantic alignment and produce more pertinent answers in Portuguese educational QA scenarios.