Jews have been drinking coffee and tea for numerous generations with few problems. I believe coffee was popular and available from about the time of the tsfat kabbalists 500 years ago. In Eastern Europe tea was more popular. On this subject, does anyone have any anecdotes about gedolim of today or the past drinking coffee or tea?
Perhaps you could allow your son to drink two cups of coffee or tea a day if he needs energy, as long as he doesn’t drink the second cup past noon or 1pm?
However, he thing about caffeine is that it can easily disrupt sleep, and teenagers need way more sleep than they get. Teenagers are biologically programmed to want to stay up late and sleep in late. But the school schedule forces them to get up early. So what they really need to do is go to bed really early, like 9pm, even though they don’t feel like it.
There’s also the possibility that stimulant use (such as caffeine) can lead to anxiety or other psychological or behavioral problems. After all, teenagers are moody and their brains are still developing.
A better way to have more energy and concentrate very well is to get aerobic exercise. Studies show it’s more effective and longer-lasting that caffeine, and it increases mood (not to mention making you healthy and preventing obesity). Teens should get up and run around every hour or two to get their energy levels up, and maybe have a quick snack to compensate for the calories they burned.