My DD is in Y10 and she is okay with physics. She understands all the basics but not always capable of solving advanced questions. The materials that I can buy are two extremes: either covering the basics, which she already has; or the very challenging materials preparing students for the olympiad. Are there any resources (courses, books, etc.) to improve students like her? We try not to use private tutor because they are so expensive and not all good. Thanks in advance.