A summer school typically enrolls students at school and sometimes university level from around the country in which it is held or even internationally. They often offer programs that are not found in public school systems, like advanced music and art classes, gymnastics, astronomy, language immersion, etc. They are sometimes called camps, but do not offer any of the traditional camping activities, and so they are excluded from the summer camps listings. For hybrid summer educational facilities that offer more summer 'camping' activities see Category:Summer camps.