How can current assessments (such as standardized testing) be biased against students who are not native speakers of English?

 Watch the webcast, Assessment of English Language Learners (Links to an external site.), featuring Dr. Lorraine Valdez Pierce. 

https://www.colorincolorado.org/webcast/assessment-english-language-learners

How can current assessments (such as standardized testing) be biased against students who are not native speakers of English? Suppose you were teaching a unit on the water cycle. The unit focused on teaching the students the parts of the water cycle which include: precipitation, evaporation, and condensation. Describe one way that you may evaluate your ELLs using a formative and a performance-based assessment in the classroom based on this lesson topic and how these assessments can provide greater opportunities for ELLs to show their acquired knowledge with minimal interference due to a language barrier.