Imacs have networks accounts , but are not in OD

I have 260 plus Imacs running 10.5 connecting to a 10.5 server. i can add the server to the directory utility and have network accounts login on all the imacs. so far , i have only had one computer actually add to OD. Im very new at this and and had the server setup dumped on my lap. have i missed a step ? any help is much appreciated. Ive done all i can looking in books and on the internet.