Japanese Level 1

I’ve started to teach a Japanese Level 1 class since last week. Before this job offer, I experienced teaching Japanese at the International Society. As the institution’s name suggests, all of my students were non-English native speakers. However this time, I teach at a local language institution so all my students are British. Among non-native speakers, speaking English is rather relaxing. However it’s a bit hard for me to speak English in front of British people as a teacher.
I started to explain with how to introduce your name in Japanese. I explained it as usual and said, “As the characteristic of Japanese grammar, the verb comes last. So, you say Watashi wa Eriko desu, and Watashi refers to ‘I’. Wa is a topic marker and desu refers to the be-verb.” However, the students seemed to not understand what I said and asked me, “desu refers to ‘am’?” So I said, “Yes, desu refers to ‘am’ and other be-verbs.” After the class, I noticed that English native speakers do not refer to them as the be-verb. It’s the word for non-native speakers to understand English grammar. This week I found out that the word “copula” in the textbook refers to the b-verb, however my students said “Never heard of it.” Finally they said, “the be-verb make sense, no problem.”