been there done that. You need that behavioral assesment. Then you can get a BIP that makes sense.
Things I have tried with mine that may help are:
1. Have a "safe place" at the school that difficult child can go to in times of emotional overload.(I found that emotional overload is usually the root cause of ODD behavior in my difficult child.) Have it written that either the child or teacher can initiate going to the safe place.
2. Make sure that the teachers know to NEVER touch difficult child when in aggitated state.(It makes them worse. And yes, my difficult child had teachers try to pull her from under desks, etc.)
3. Make sure that the teachers always use a calm voice with difficult child. Elevated tones of voice evoke emotional response which makes things worse.
My last suggestion is that ODD is rarely a diagnosis by itself. Have you had a complete, multidisciplinary evaluation done on difficult child? If not I would suggest it. My difficult child's diagnosis has changed several times, and now the ODD is off, replaced by Aspergers.
I could pm or email you a BIP we used for my difficult child if you like, so you have a sample. Just remember that it would be a sample, and would just give you some ideas.
Hang in there.