We hold English classes every Tuesday and Thursday evening from 6-8 PM in four levels - Basic (Newcomer) and Levels 1-3. We have teachers for each class but frequently one or more has a conflict and we need substitutes to fill in for them. We have teacher manuals with detailed guidance on how to present the material, and the teachers leave an update after each class covering what they did and what page they are on in the textbooks.
Because we enroll students all year long we frequently need to work one on one with students to catch them up with the class they join and this is a way to fill a need even when we don't need a substitute!