Are there any scholarship benefits for World War 1 grandchildren?

No. At least none based on the service of the greatgrandparent. But there are many scholarships out there, some based on need, some based on merit, and some based on where you live, what high school you attended, your intended subject of study or other qualifying factors. One of the useful things your school guidance counselor can do is help you identify scholarships for which you are eligible, and help you go after them. Some of them have few applicants because they are restrictive about who can apply, so you would want to find any of those for which you might be eligible, and apply early. I urge you to get started on the financial aid process as soon as possible. You must fill out and submit the FAF so your need can be determined and you become eligible for government grants and possibly low interest loans. Don't wait to do this. If you are a senior, start just as soon as you possibly can. Best of luck.