Never go into your classroom empty-handed. You must use a variety of teaching tools to keep an ESL class, especially a large one of 75 students, enthralled with the lesson.
For a standard 45-minute period, plan activities and drills that will last for no more than five minutes each. Possible elements include warm-up, review, new vocabulary, current events, grammar quiz, group singing, conversation in pairs, pronunciation drills, new vocabulary practice and charades.
In order to teach your ESL students, you need to know as much about them as possible. Begin with questions about why they are studying ESL. Do they need English language skills for school, work, church, community or home? Can they already write and read English? Do they write emails or text messages in English? Can they talk on the telephone or understand movies in English? Do they need to study for a drivers test, citizenship test, or TOEFL exam?
Consider giving your students a quiz early in the course, to determine whether they are beginner, intermediate or advanced students. Then you will know better how to meet their individual needs within the structure of a large class.
With 75 students, the more advanced ESL learners will be able to help the ones who may be struggling. Divide into groups of four to six students each to practice conversation, solve problems or read for comprehension, reporting content back to the class. Solve a mystery. Plan a community garden. Develop a class choir, in which volunteers rehears and perform a concert for the rest of the class. Singing is one of the best ways to learn English.
You can listen for grammatical errors, pronunciation problems and other issues while your students are working together. Don't jump in and start correcting them; give them a chance to correct each other. Then gently work on problem areas you have observed, without embarrassing anyone.
Teaching 75 ESL students at one time will go much more smoothly if you remember to plan your classes, get to know your students, and let them help each other to learn.