I am teaching ESL to high school students and I am trying to find a good way to assess their listening skills. I find it difficult to truly assess listening because there are many other factors that can make it seem like the students is not hearing the English correctly. Any ideas?

Is it just the English that they are not listening to, or are they not wanting to listen to you at all? When it comes to the FT's class they often think it is chill out time. I sometimes start by saying sentences to random students in my elementary Mandarin and asking them to repeat but in English- I find it does make the whole class sit up and listen. The BBC listening audio with text that you can print out is really good stuff for listening and there is often lines for half a dozen students-so lots of interaction. It all depends how quickly you need to assess your students?