What could the possible reasons be that assessment is neglected in Performing Arts and Music in the Foundation Phase?

most people regard art in education as a luxury and don't see the importance of it, they don't think that creative activities like painting, dancing or learning how to play music is important. these activity helps  a child develop motor skills, language and cognitive development. Mathematics, languages or science are not the only subjects that should be give attention art should be given as much attention as other subjects

explain how you would advocate for and heighten awareness about the importance of assessment when speaking with your HOD about your concerns in this regard.

I would show the HOD the results and researches from other school how art has improved the learners language, when learners make art or just talk about it provides opportunities to learn words for colors, shapes and actions. In Foundation Phase children can use descriptive words to discuss their own creations. It will help develop their decision making,  strengthens problem-solving and critical-thinking skills. The experience of making decisions and choices when creating a piece of art carries over into other parts of life. If they are exploring and thinking and experimenting and trying new ideas, then creativity has a chance to blossom. It will improve their academic performance children  who participate regularly in the arts are more likely to be recognized for academic achievement, to  participate in a math and science fair or to win an award for writing an essay or poem than children who do not participate. Art does not only improve all the things but it also improve a child's mood and reduce chance of depression.