I've never used them in teaching but I used to paint with
them all the time. I used Luma Inks. If you don't want the
colors to fade over time check to see how lightfast the
colors are. Only a few of Lumas many, many colors are safe
from fading. I loved the liquid colors and worked for years
with only six colors. Matthew Monks introduced them to me
in about 1968. I only switched to tube watercolors a few
years ago. I used the round plastic plates that came with
diet dinners for palettes. Biggest disadvantage with the
liquid colors is that they don't lift. All of them are staining
pigments. I was always amazed how far just a few drops
would go and how long the bottles lasted me. I doubt that
would be the case with children using them.
Woody in KC
All five paintings on this page were done with Luma inks:
http://www.taospaint.com/WoodysArt.html