sensitivity

Audiophile Music Teacher should not only teach music but the way it's being played through the system.

Sounds to me like you could use "compression." See if school will spring for inexpensive "compander" (compression-expander in one unit) like a used DBX 2BX on eBay. Once popular in '70s, out of favor now because CDs have more than enough dynamic range. What you want is less dynamic range (or compression) at low volume levels to reduce peak dynamic range levels at low volumes & people usually play music loud enough not to need expansion. Installs easily in tape monitor loop. Good luck.

You can probably read better definitions than I could give you on "compression-expansion" on WWW or in product description at eBay.

One thing that comes to mind is dirty switches. Do you hear "crackling" when you turn the volume knob or when pushing any source buttons? If so, some contact cleaner may solve your issue. Another suggestion is if there is a mute or attenuation switch, use it and you'll be able to turn the volume knob up more. If your CD player has a gain control you could try cutting back the input signal which would allow you to turn the amp volume up as well.