one of the things that schools are doing that we are working

原句是不是应该是one of the things is that schools are doing that we are working
如果是这样的话,第一个that不能去,因为引导的是表语从句.第二个that能去,它引导的是宾语从句.
你记住,that在主语/定语（that作从句的主语)/表语/同位语从句中绝对不能省!