It is thick tea, koicha, [濃茶] that is “tea proper”. Proper thick tea is mid-way between a liquid and a paste. It can only be blended [練(ね)る], using a bamboo whisk cut into tines that are fewer, and consequently thicker and stronger. Even for a single guest’s serving, the volume of powder required is such that, upon contact with that powder, the temperature of heated water immediately drops.
Schools of Japanese tea ceremony are not institutions in the way we envision a contemporary school as a high school or university. There are teachers, but they are not bound by a curriculum. Nor do students gather at a schoolhouse where teachers teach classes on various aspects of the tradition.