You can start when your child is finishing elementary school or in middle school.
Biology homework helps speed up the learning process, but it really depends on your level of self-discipline. This is especially true because biology involves a lot of new definitions and classifications.
If you what to take your biology education to the next level, then teach it, but if you what to really get the best quality of tutoring, then learn from an older tutor with teaching experience.
Just trust the process, all you need to do is be ready to learn. In time both of you will fall into a nice routine.
Medical Science, Botany, and Zoology.
You can try on your own to memorize the terms and concepts used in biology, but until a tutor shows you the connections between these concepts, you’re not genuinely learning biology.