Assuming your correct the wiring, you can reduce the strain on the amp with additional cooling.
I had my amp in a very tight space where it clearly would not get enough air circulation, so I added two computer fans to the top drawing air out.
In my case, the Amp had a
Switched Electrical Outlet on the back, so when I turned the amp on the Fans came on automatically. There are 12v computer fans which I ran at between 7.5v and 9v. This was still enough cooling but the fans ran quieter, which mattered in my living room.
While you are investigating the integrity of the wiring
(no stray strands) also investigate the
correctness of it. All wire as a mark on one of the wires, sometime a ridge, sometimes embossed printing, sometimes actual printing, other times a stripe, but one wire is absolutely marked. That Marked Wire should be consistent through out the system. If the Marked Wire in on the Red+ at the amp, then it should be on the Red+ of each speaker.
You previously said -
> However the teacher when it was last used had it 3 quarters of the way she said - I didn't see it, but I would imagine that would be around 1 o clock.
Quibbling but 3/4 volume is closer to 2 o'clock or 3 o'clock which is likely in excess of 100dB or to put it another way -
WAY TOO LOUD!
The speaker impedance is something of a problem but at normal volumes under 12 o'clock, is perhaps less of a problem. This is about CURRENT. The lower the Impedance, the higher the Current, and the higher the Current, the more Heat is generated. More heat equals more strain and more danger to the equipment, both speakers and amp.
So among other things, you might want to inform the teachers that there is a limit to how loud they should set the volume control. Make sure they understand that about 12 o'clock is the Maximum, NOT the ideal.
Again, in my experience, when you get up to 1 o'clock or more you are at or in excess of 100dB which is VERY loud, especially for children with tender ears. Likely if
Health&Safety came around, you would be in trouble for reaching those volume for more than a couple of minutes.
Here is a test I ran for other unrelated purposes -
Next using my turntable and the Hendrix LP, I tested the volume from 9 o'clock up to 1 o'clock
Hendrix - Stone Free
9 o'clock = 75dB
10 o'clock = 85db
11 o'clock = 90db
12 o'clock = 94db
1 o'clock = 98db
Though I had somewhat larger speakers, this somewhat confirms that there is really no need to be over 12 o'clock on the volume dial.
Hope that's helpful.
Steve/bluewizard