The school lab experiment I've described above was both dangerous and unofficial in that it was not sanctioned or supervised by a qualified teacher and I would strongly suggest no one attempts it (or anything similar). Moreover, these days, in many jurisdictions it will likely be unlawful†. My message is do not try it both for your own safety and that in this hypersensitive, overly-political world you will draw the ire of others!
† Back then—decades ago in much simpler times—this would not have been the case for small lab quantities although it likely would have drawn the ire of the chemistry teacher—not so much because of the material's intrinsic dangers—as then, there were many dangerous chemicals that were both commonly available and easily obtainable without authority (and that are now no longer available)—but rather because he'd have deemed we'd not have had sufficient experience to do it safely.
(Those were the days when black powder was not only made in the lab and the teacher demonstrated the method and we tested the result but also we had to know the chemical equations and work out the optimal ratio of the three ingredients as part of the chemistry curriculum.)
Now, you perhaps think me a lunatic or at least stupidly reckless. Perhaps so, but I did give it considerable forethought and I'm still here complete with all my bodily bits.
No, I'm not going to go into explicit details for obvious reasons but I'll say this much. I made the smallest amount that was practical to make and I achieved this by measuring the reagents out with an eye dropper. I chose the narrowest test tube I could get as the nitro separates out into a layer and I had to have sufficient product to cover the CSA of the test tube (so I could see its meniscus). Oh, and the lab gear was very clean and I used BP-grade reagents to stop any contamination. (In those days, we had important/key reagents in BP-grade at school as we budding chemists were expected to know their taste (but only BP-grade was used for this purpose). They were diluted to a weak N/40 or so and we tasted them! Can you imagine that ever happening now? Not likely, oh how we overprotect our poor little darlings these days.)
I carried out the reaction in winter which meant the reagents had to be heated to the recommended reaction temperature which was only a few degrees above the lab's ambient (it was easier to heat up the large bottles of regents rather than cool them). I was careful to hold the recommended reaction temperature as accurately as I could but it wasn't difficult with the reaction being only a little above ambient.
Everything went according to plan and it was done according to book (this included even cleaning (neutralizing) the final product with sodium carbonate to eliminate residual acid (from one of the reagents).
Did it go bang as expected? Yes! Was anything damaged? Nothing during manufacture, and nothing of any consequence during testing. Did the chemistry teacher find out? No! Did other kids participate? Yes, two others (but for some reason they quickly left the lab when I mixing the reagents). How did I know what to do? The procedure was well documented in a large general book on organic chemistry of about 800 pages given to me by my father. It described dozens of chemical processes in detail such a Haber's nitrogen fixing and how to make various nasties, such as HCN, in industrial quantities. Whilst it may not seem like it, I was reasonably responsible around chemicals and I still am.