How should I assess the content knowledge, understanding and skills of my ESL students?

Using rubrics could help you. If you are familiar with Rubistar, try to download it. This application can help you a lot.

There is not always one unified or accurate way to asses their skills but rubrics and performance criteria is a great way to assess a variety of student workut. 

I think its mandatory cause employers or teachers don't know ESL student's knowledge and skill before providing a job or giving a lecture. 

" Open Ears can because it is the sign of open heart, appreciating, helping attitude".

Language is a big issue for some students who are from rural or remote areas.

Hear without any bias. Read with patience.

The accent may differ but give importance to the idea of discussion.

 

Thru various tests, speaking exercises, thu written and oral skill testing