Reddit mentions of SE - Loupe - Doublet, Chrome Plated, Round Body, 30x-21mm - MJ361830C

I highly recommend the Hakko 936 soldering iron Hakko 888 soldering iron, which is still actually available. It's hard to fathom how a $100 soldering iron could be that much better than a $20 one, but once you start doing anything more serious than just sticking some wires together, it's worth it.

As for other tools,

• Standard needle nose, dikes, and pliers set
  
• Tweezers - Additionally plastic ones if you're going to do PCB etching.
  
• Dental Picks - for positioning surface mount parts and pushing wires into molten solder.
  
• Wire strippers - You'll often see people using the combo wire stripper / crimpers. They're not as nice as a real pair of strippers.
  
• +/-12V power supply for basic analog electronics, 5V for digital work
  
• Breadboard
  
• Solder sucker - Copper braid is useful for the same thing, but given the choice of the two, I prefer the sucker to undo soldered joints.
  
• 30x Jewelers Loupe - Mostly useful for surface mount work, but pretty much all soldering is easier when you're able to look at it.
  
  As for components, I've been buying them piece-meal for years, so other's will probably be able to yield you a better recommendation for kits than anything I can find just from a quick search. I do mostly digital work, so as far as passives, my main stock is:
  
  
• 0.1uF and 100uF capacitors, 25V
  
• 100, 330, 1k, 4.7k, 10k, 100k, 1M resistors
  
  If I need any other resistor for a specific project, I'll tend to just buy an extra 10 and keep them in labeled coin envelopes.
  
  Random other pieces:
  
  
• Precut Breadboard jumper wires
  
• 7805 - 1A 5V linear regulators
  
• 1N4007 diodes
  
• 1N4148 small signal diodes
  
• 3V linear regulators if you do low power work (MSP430, etc)
  
• An Arduino - If not for real projects, I use this a lot to hack together crude digital signal generators to test other chips.
  
• LEDs - I found a good deal on bright red ones, but any will do
  
• push buttons, power switches, DIP switches (4 in a tiny package that fits in breadboards)
  
• Copper clad perf board - To make through-hole projects permanent. Be careful because this also comes without the copper pads, which is just more of a pain in the ass to use.
  
• Copper Solder braid
  
  Edit: Fixed the soldering iron model.
  
  Disclaimer: I'm using my Amazon Associate links for all of these, which always feel a little amoral and a conflict of interest, but really, if my apartment were to go up in flames and I could afford it, I'd buy every link on this list right now. Does anyone have strong opinions one way or the other on using them?

All three can be had for cheap from amazon, which is where I got all mine. Check out the links below... It's the setup I have for even cheaper than I paid (closer to $15). Acid is pretty standard and you can't really get "bad" acid (Gerry Garcia may say otheriwse). The scale has been awesome to me (the reviews on amazon are good too). The loupe is pretty cool and has been pretty helpful. It's just a magnifying glass. As such, it's hard to fuck up.

Acid Test Kit

Scale

Loupe

For the majority of the time, if you just want a good look at your crystals (for example, if you're trying to determine if you have single crystals suitable for diffraction crystallography), a simple jewelers magnifying lens or a similar magnifying lens (~10x) is often acceptable. Often that level of magnification will be enough for just looking at your crystals and describing them. I don't know that much about photography so I can't be too much of a help there. High-magnification optical microscopes get expensive pretty quickly, and they won't be able to tell you a whole lot more than your cheap, $2 lens will.

You could buy a few sets of snap circuits for teaching electricity. They have all kinds of neat components and hundreds of project guides, and the kids can design their own circuits to study things like parallel vs. serial, resistors and capacitors, etc. It would let them experiment with electricity and circuit design without having to fool with things like soldering or breadboards, so the projects could easily be done during a single class.

For biology, maybe some good models - skeleton, heart, etc. and charts/diagrams. The same for geology/earth science, get some good rock samples and large diagrams.

If you can't afford/don't want to get everyone microscopes (or maybe even if you do), get some 30x jeweler's loupes for looking at leaves, bugs, rocks, etc. You can get them for about $4/ea.