Many children struggle with high school science. Science is still seen as one of the harder subjects (along with maths), and the sheer depth of the subject can be overwhelming.
Children that are struggling with a subject like high school science are often slow to tell their parents about it. Often they get so far behind in a subject that when they do eventually seek help it's too late.
High school science lays the groundwork for a lot of varied careers. It's a rich, rewarding but also demanding area of study. Sometimes a student just needs a little extra help to grasp some of the core concepts and a lot of the more advanced areas of high school science that they are struggling with will fall into place.