It comes about because counties with a rich tax base (e.g. Los Alamos) can afford good schools with all the latest classroom tools like computers. Much poorer counties, like Rio Arriba, struggle just to pay teachers who often have to buy their own classroom supplies. A distribution system to somewhat equalize the system statewide was shot down by a judge who directed the legislature to come up with a better one so that kids statewide have equal opportunities.
Of course, it won't work because it's up to the parents to manage and support their child's progress in school. In the poorer counties, they most often have single parent homes and the child may not be given guidance or help and often he/she becomes more disinterested in school as they get older.
Down here in the oil patch, where good jobs are plentiful, parents want the same for their children, even those where English is a second language (and many oilfield jobs are staffed by non-English speaking men). With the rich tax base from oil/gas drilling and production we are building new schools, new sports facilities and now a new vocational/technical facility is in development to train workers that don't need or want a college education. A family I'm friends with just had their daughter graduate from Junior College last May a week before her high school graduation. She is now in a four year college starting as an advanced sophomore or junior.
Thanks for the explanation.