We are raising chicks for 4-H and they told us that only Cornish Rocks, Jumbo Cornish, and Cornish type crosses are considered 'meat' birds.
Rhode Island Reds will NOT be slaughter size by a month and a half. They grow slowly, because they are egg layers, not meat birds. RIR's typically take 8-10 weeks to be close to 'full size', and then another 8-10 weeks to begin laying.
You might want to look into talking to your FFA project leader, because RIR's arent even classified as a 'dual purpose' chicken, so I still dont see how they can classify them as a meat bird. They are known for laying, and are some of the best layers I've heard of.
We are actually getting some to add to our laying flock. Good luck. Maybe I misunderstood you, but I even looked at the FFA info online, and it seems to go in another direction. My children will be joining FFA too, so I would be interested in hearing that any bird could be classified as a meat bird, because we have extra cockerels.