I am totally guilty of this as a teacher – doing work or talking to another teacher in the room while my students are working. Though I make sure to keep my eyes open for any raised hands. But the thing about students like ours, is that more often than not they are not confident in their English level, or don’t want to be seen asking for help, so if they have a question, they are not going to raise their hand to ask you.
Once the kids get to work makes sure you do a couple of laps around the class. Check-in with your students and ask them how it’s going. Though they won’t seek you out to make conversation they won’t have a problem chatting with you if you go up to them.