My 14 year old son is heading for Eagle and just completed his Nuclear Science merit badge in a few weeks. Has only been in Scouting for a year and is about to go Star, with 16 merit badges, 7 of them Eagle.
Both he and his older sister (16) are working toward GED, and we now have to go to the district to get approval for them to take it early. I just got two sets of review books for them to work through as preparation, and what a breeze. They had it all down by sixth grade (thank you A Beka).
His toughest part of making Eagle is ahead of him and that id the Eagle Project. Work with his Scoutmaster, the troop committe, and the Scout District Advancement Chair to make sure that he follows the rules. When he starts he needs to track all the time that he spends, making phone calls (even just leaving a voice mail), time you spend driving him to, waiting for him, driving him back from any coordination, etc. Have him track and acount for every single minute for every person that helps.