In-person or online, you can help kids of all ages with their homework, projects, or exams. If you get the word out, you may be able to host tutoring or study groups for more than one student, all of whom pay you by the hour.
If you have expertise in a subject, field, or niche, then creating an online course is a great way to earn income. There is a bit of work to do upfront to create the curriculum, record the teaching and perhaps have handouts or printables.
This is a nonprofit online learning database filled with free lectures and information for students of all ages and grades. You do NOT have to be a teacher to work for them, and you can make a decent hourly wage.