From colleges, high-school and Universities, the high reliance of school grades can't be over emphasized. Yes, its possible to change grades and hackers have changed grades multiple times from different schools and this was confirm from an article with a verify source. There is no doubt that a hacker could potentially change your grades. If a hacker had access to your personal information, such as your grades, they could change them to whatever they wanted. This could have serious implications on your future, and you may not be able to get your grades back if this happens. It is important to keep your personal information safe, and make sure that only trusted people have access to it. If you are ever worried about your grades being changed, talk to your professor or school staff about the matter.