Where do I report private music lesson income if my normal job is teaching music in the public schools? I don't consider this income "small business" or "self-employed."

I teach music in the public school system for my "9-5" job but I also teach some students private music lessons at my home after business hours and during the summer. I don't consider this extra income as "self-employment" or "small business income" because it is tied directly to my normal job and is not my main source of income. Can you tell me how I should report this extra income? Last year, I made just over $12,000 with these extra lessons.