Dear Sir or Madam,
I am a junior student at Beijing Institute of Physical Education, majoring in children physical education. I am writing to ask if there are any part-time job vacancies at your kindergarten.
I have had some experience of working as a teaching assistant for physical education over the past three years. I will be able to provide references from my teachers at the university. I would prefer to work in the afternoons, as I have classes in the mornings, and I can start from the beginning of September.
I am looking forward to hearing from you in the near future.