I am volunteering to bake two full sheet cakes for our school's 55th anniversary. I am looking for ideas for these cakes. I really want to make them special since I had nterned at this school 31 years ago, and I have taught at this school for the past 7 years. Please help me and share your wonderful ideas. Thank you for your help.

Well I'll take a stab at some ideas for you.
To reduce the amount of decorating make a frame of icing (even just shell border) about 2-3" from the edges. Can trace around a 1/2 sheet pan.
Between the cake edge & this frame you can fill in w/cornelli lace; jimmies or other sprinkles; or airbrush a color. Do your writing in the center area in fancy script. Put roses &/or other flowers on two corners of the frame.

Make a big fondant (or gp or colorflow or cookie) '55' to stand up in the center of the cake. If the school name isn't very long maybe do it also. The name could be laid on the cake instead of standing up.
Or make the four '55's to stand in each corner centered in a floral grouping. The name of the school can go in the center w/congratulations?
Flowers can be in the school colors.

Thanks a lot for your ideas. I've been looking at some of the sheet cakes, and I was also thing about writing "Congratulation on 55 years of excellence" in the center of the cake and make either lattice or corelli lace around the center. Maybe doing lattice or basketweave around the base. I want to make it look different than a store bought cake.