Here is some anecdotal experience. My son goes to this school mentioned in the article. And it is a good school, with some seriously good teachers, from my personal experience. This school and many other schools have been taking in "economically weaker sections" or EWS kids from some time now, but not more than some 5 to 10%. Also, different schools had different models for inclusion. The Delhi Public School, I believe holds special evening classes for these kids, whereas other schools like to integrate them into the main class.
The specific experiment described in this article actually took effect in this school year and has raised the proportion of these kids in the class to 25%. Of course, I am not privy to whatever internal issues the teachers/kids have been having, but its early days still. The no-testing admission has been the law in Delhi for some time now, but now has become law across the nation (I hear that private school admission in Bombay is even more difficult than Delhi). Most of the schools are incensed at having their own policies superseded arbitrarily by the law; hence the resistance. However, I am fairly certain that they will adjust to this and do a good job, once the initial issues are ironed out.
From my own personal experience there are two issues to deal with. First is the rich poor divide. Compared to many of the parents in this school, I am decidedly on the poorer side; these are the parents who own farm-houses in Delhi (about USD 10 million apiece) and send their 5 year olds to the south of France for summer vacation. My family got to go to the hills near Shimla, overnight journey by train. The first time I took my son to one of his friend's birthdays my jaw fell open. As a middle class parent with a middle class upbringing, I am having the same conversation about rich-poor divides with my son when I plan his next birthday party. I simply cannot afford to match his friends birthdays and, even if I could, have no intention of doing it. In my opinion, this is an important purpose of school; my child needs to learn the importance of money but not to make the mistake of conflating it with self-worth; he needs to learn to get along with all people, both richer and poorer than him.
In short, by having EWS students in the school, they are not creating a new problem; however, of course the EWS parents and children feel it more keenly and probably need counseling on how to deal with it.
The second issue is the eagerness for an education and the ability to follow that through. IMHO this is the most serious problem: most of the other kids in school have parents who are genuinely motivated that their children get an education and have the ability to help their children, either directly or by hiring tutors. This is the place where the EWS parents suffer the most and they need the most help. In many cases, they simply need reassurance; it is often the case where the kid is lagging behind a little in something or the other, but within the overall is well within the group limits; given time he or she will catch up. However, the parent panics when they hear about it from the teacher and start that "all work no play" nonsense alluded to in the article. Which actually increases the pressure on the child and makes things worse. I think this is where we parents can actually help, by forming support groups and reaching out to the EWS parents. However, this is the kind of thing which can't be legislated and takes time. The schools can probably also reach out to the parents (the Shri Ram school has a parent teacher association, but I am not aware if they are directly dealing with the issue) for help. Once again, all of this will take time.