Every day well-intentioned language teachers go into class and sabotage their students’ learning.
They do it unconsciously, without even realizing. They do it by not monitoring the language they use when talking to students. Language that is;
Too difficult (too much unknown vocabulary, too colloquial, etc)
Way too fast
Too many discourse markers (um, er, y’know, OK, etc.)
Echoing (repeating the students’ answers back to them for no reason)
I’ve observed a couple of teachers who had at least seven uses for the word ‘OK’ (start / that’s fine / yes / no / stop / do you understand? / good).
It’s easy to fix.
Take a voice recorder into class with you (most smartphones can record a class, without an issue). Record your lesson, and listen to it later. Listen to it from the point of view of one of your students.
Does it make sense? Does it even annoy you? Have you got any annoying speech habits? Use the above list as a checklist, and put yourself in the shoes of one of your students.
Do your students a favour, and give your classroom language a tune-up.