All students are encouraged to participated in exams and eisteddfod competitions. I can teach you all the techniques and repertoire in the world but when you get out there, you gain the experience and learn from watching others. Year after year you will see significant improvement in their presence and confidence.
There are also quite a lot of my students who don't do competitions. We do continue to document and record the development of their voices. You will see results very clearly if you are determined to work on it.