School suspended child. Child now depressed. What action can we take?

Immediately inform to the concerned police in writing. After the same issue legal notice to them. Hopefully by these actions your problem will be solved of not then initiate legal process against the school authority.

approach to the nearest police station.
meet S.J.P.U. officer.
share your concern with him/her. they(officers) will help you to resolve the issue.
in case you don't want criminal action against the school,
initiate civil remedy by sending them legal notice.

You could consider filing a complaint with the Child welfare Committee against the policies of the school or even against the principal if you feel necessary. Taking action under the penal laws would be difficult.

Regards