Final answer:
The nursing model referred to as the "class without walls" is the Career ladder model.
Step-by-step explanation:
The nursing model that is referred to as the "class without walls" is the Career ladder model. The career ladder model is a concept in nursing education that allows nurses to progress through different levels of education and training to advance in their careers. It is called the "class without walls" because it provides flexibility for nurses to continue their education and gain new skills while working in a healthcare setting.