Among many things that British got wrong, one was the refusal to call a place school if it did not have a permanent building neatly separated into classrooms and such. More than the learning outcomes, the infra that mattered more for British to recognize anything as a school and they went about closing down the informal "under the tree" schools in this manner. Of course as you go deeper you realize this policy was driven more by the corruption in the East India Company and British government where missionaries wanted funding from government to build "infra" in the same of schools.
Much later in 2005 or so James Tooley another British Economist in charge of World Bank aid to school system in India discovered similar trends and quit his job to promote low cost high quality private schools.
Indian government around that time brought an evil law called Right to Education and permanently killed this concept. Running an open air school in India might get you jailed today.