Hey, if a teen is knitting in public, way to go! Seems every generation says "what's with teenagers these days?", being one of the 80's the grownups freaked out over us wanting to look like Madonna or punk rockers. I think they have it harder these days so anything they do alone or as a group that is satisfying, educational, calming, and even good for society if you're doing it for charity, then DO IT and tthhhhpppbbbtttt to those that give ya weird looks. I'd say always ask if it's ok if it's a situation you may think someone would have a problem...like a teacher or lecturer, you may be doing it quietly but they may wish to know you are paying attention to them and even though you can be, eye contact tells people you most likely are... some folks are sensitive that way. I had a professor in college whose biology class was so huge, even if 20 people were missing, some would have a friend bring a mini recorder to his desk and he'd line them up, sometimes a dozen or so, he didn't care... he got paid and it was our tuition that was being forked over, so if we couldn't get our butts out of bed to show up, it was no skin of his nose.