Combining the two sentences by using a correlative coordinator: The conference on nuclear energy was not attended by students from Stanford. We were very disappointed that the conference on nuclear energy was only teacher from Berkeley.

Combining the two sentences by using a correlative coordinator: The conference on nuclear energy was not attended by students from Stanford. We were very disappointed that the conference on nuclear energy was only teacher from Berkeley.

We were very disappointed that the conference on nuclear energy was not attended by students from Stanford, rather only teachers from Berkeley.