I have used the quiz-making learning tool within gemini. It is very good for things that would exist in a typical K-12 textbook. The first 30 or 40 multiple choice questions on a subject are usually pretty good and useful. But then it will tend to repeat multiple choice answers, give strictly wrong answers, repeat questions, or offer multiple valid answers. The answer explanations are what you'd expect with little human QA. Still a useful tool for people who sanity-check the given answers, but it might do more harm than good if people don't follow up on their confusion.