Should you use a student's native language when teaching English?

Occasions when I incorporated home language into ESL teaching:

I was teaching elementary school children and used English solely in class. My educational assistant spoke Thai, Lao, and English. I often asked her to use Lao if the Laotian kindergarten and 1st grade students were feeling stressed or upset about being immersed in such a new and frightening environment (new to an English speaking environment, surrounded by linguistically and culturally different children).
Same job: when teaching the 3–4–5 graders social sciences and sciences and math terms and reading those texts with them, their homework was to go home and explain what they had understood about the subject to their parents in their home language, and then seek out an older student who knew more English and have a first language discussion about what we had read.
In high school (secondary school), the students were dropped into monolingual English classes. I was teaching Spanish speakers, so I bought the same textbooks in Spanish, whenever possible, in the same subjects—history, physics, biology—and their homework was to go home and study the chapter we had covered in English that day.
I did not use home language in any way when I was teaching EFL (students were living in their home country).