I think it's best to give students comprehension questions in English (L2) to verify understanding, but what happens when the question or portion you want to verify is too difficult for their English level? For example infered meaning or something that wasn't factual in the reading or conversation that requires them to make assumptions.

I've attended a couple JHS lessons where the teacher did all of the comprehension checks in L1. Most of the time I was standing there thinking, 'You could ask that question in English!' However, some of the questions would have been difficult for students to understand if possed in English, so I couldn't say the teacher should refrain from using L1 totally.

What do you think? Should all the questions be in L2? L1? Is it OK to mix L1 and L2 when where checking understanding? Should we just eliminate questions that may be too difficult?

If you're talking about a worksheet or test, you may want to provide an "I don't understand the question" option. With that, maybe they could check the "I don't understand box" then raise their hand and receive a copy of the question in L1, with a point reduction, of course.

I think in terms of spoken English, it is important that there is some L1. Often I will ask my students what something means in their L1, which I can understand.

I don't use the L1 myself, just get the students to do it.

Does that make sense?