‘Teenagers are too young to teach other people about anything.’ Some people might think that teenagers are not well prepared to teach anything to anyone, but I disagree. From my point of view, this way of thinking is not only patronising(1), but also old-fashioned. On the one hand, teenagers and young people (often)(2) know more about technology than adults and, for instance, a lot of us have had to teach our parents how to use new technology. On the other hand, young people, such as teenagers, are more aware of environmental problems than grown-ups, or old people, even though adults are usually not interested in these issues because they think it is not important.(3) Teenagers would disagree. Because of the internet, teenagers know more about the stuff they are interested in than their parents did when they were their age. Thanks to the internet, and their curiosity, they are well-prepared to teach others about the stuff/things that they know. (1) In British English it is spelt patronising, but it might be different in the US. (2) I've suggested "often" here because I think it's a sweeping statement to say that young people always no more about technology. Bill Gates, or mark Zuckerberg, might be good examples. (3) This is a bit of a run-on sentence. Perhaps something like this would be better: On the other hand young people are more aware of environmental problems than adults. Particularly as adults don't seem to be very interested in these issues. Note, also, that the on the one hand, on the other hand usage isn't quite right. It's used to describe conflicting things. You've used it to show two things that teenagers do well. An example of proper use would be: On the one hand teenagers are better with technology. On the other hand adults have more life experience. In this case you are giving two different views to an argument. I hope that makes sense?

‘Teenagers are too young to teach other people about anything.’ Some people may think that teenagers are not well prepared to teach anything to anyone, but I disagree. From my point of view, this way of thinking is not only patronizing but also old-fashioned. On the one hand, teenagers and young people know more about technology than adults and, for instance, a lot of us have had to teach our parents how to use new technology. On the other hand, young people such as teenagers are more aware of environmental problems than grown-ups or old people, and furthermore, adults are usually not interested in these issues perhaps because they think they are not important. Teenager would disagree. Because of the internet, nowadays teenagers know more about stuff they are interested in than their parents when they were their age. Thanks to the good use of the internet and their curiosity, they are well-prepared to teach others about stuff they know.