A play group is simply children who get together to play.
A co-op is when the members share costs.
A pre-school is structured learning and play "school" for children aged 2-4.
Therefore, a co-op pre-school is such a school wher ethe parents share costs and responsbility, exactly as the article explained.
Something that is "glorified" (in this context) is simply a bigger, fancier version.
Take a bigger, fancier version of children who get together to play, have parents share equal responsibility, and you have a co-op pre-school.