For older children (eg teens) and for adults, you could start introducing phonetic symbols. You could start with the schwa and with sounds your students find difficult e.g. diphthongs. I don’t think it’s necessary to write down everything using the phonemic alphabet unless the students are very interested in learning it.
As for very young learners (under 10), I think it would be confusing as they are still mastering reading and writing in their own language. I suggest you avoid its use with this age group.