I agree with you that young students (primary and high school) are interested in exciting things.
And I agree that if someone goes to a school, that visually stimulating demos are better than theory and board work. Sure, liq N2 is great as are luminol, foam, colour changes, solar cells, smoke etc. Now these demos are relatively safer than demos involving fire or explosions which are more inherently potential hazards, to start with.
One problem with spectacular demos used to interest students in science is that invariably the demos have very little to do with the type of study or work that will come to follow at higher levels, so this is something to keep in mind. The promotion of science should be somewhat more balanced than just a "magic show". If the audience has no intention of becoming scientists then sure a bit of light entertainment is fine.
Second, you can see right here in this thread exactly what happens when "playing with fire". A students has seen a teacher light their hand on fire and it looked spectacular. Now this student hasn't gone out to become a scientist, they have jumped straight on the internet to try and find out how to set themselves or their friends on fire in the same manner, no doubt in a much less controlled and much less safe environment (I doubt they are going to do it in a proper lab, with good ventilation, fire extinguishers, fire blankets, sand, high pressure water, trained chemists and first aid staff and quick access to emergency services if required.).
I am not sure how old the posters are here, but you would have to be a little naive to presume that young students won't try and copy cat dangerous stunts.
By all means use flashy demos to interest students in chemistry. My point is more don't set yourself on fire, don't ignite acccelarants, don't explode things, there are plenty of other ways to get peoples attention, and if you can't get their attention without these dangerous things, then maybe they shouldn't be encouraged to be chemists in the first place. Injuries from chemicals are often really awful (burns, poisoning, blindness etc.)
Be careful, leave the experiments to your teacher or lecturer, DON'T TRY THIS AT HOME.