We’ve all had times in class when a student won’t use a structure with any confidence, despite this being the main aim of the lesson. You get to a practice activity, and you just don’t hear the “target language”.
Isn’t it frustrating saying something like “remember to use the modal verbs I just showed you”? Sometimes it’s counter-productive and can even ruin the flow of an activity, when you focus the students so much on specific language.
When I started off teaching, I used to have a little sign with “-s” on it which I’d produce to remind students about the third person singular ending – to little effect.
You can’t control exactly how your students’ language develops. While teacher interventions can speed up the process, it happens in its own way. For grammar, there is a kind of developing internal syllabus; students are constantly reviewing and refining their understanding of structures they’ve been introduced to. For vocabulary, a number of exposures to a word may be needed before it’s really internalised.
This means you can relax, let the activities run, react spontaneously to content and language that arises, and stop beating yourself up. Both you and the students will enjoy lessons more when you give up the illusion of control.