For some reason, it seems to have been difficult for poor people to spend time outdoors:

One of the most perplexing problems that parents or teachers used to face is that of the delicate school child. Some little girl had scarlet fever. She was quite well, but had been left pale and anaemic. The doctor sagely said that she should be kept in the open air. She, on the other hand, did not care to lose a year in her standing at school, and perhaps she could ill-afford to do so. Or, again, a boy whose parents were delicate began to show signs that he might have inherited some tendency to disease. Again the mandate, “Open air”; and the parents, if they were poor, were likely to reply, “Yes, but how?”

With the rich this situation was always easily handled. There are schools which make a specialty of outdoor exercise, or a child may be taken out of the classroom and sent to the country with a tutor. Neither education nor health suffers in such case, but with the poor it has been a very different matter. Their children have barely time to go through the elementary schools before they must go to work, and, in fact, only a minority of them accomplish even this; and even if it was readily decided that health is the first consideration, the only fresh air available was to be found in the streets or in parks where the all of the “gang” may come upon the child at any moment.

The solution: outdoor schools!

The ideal open air school is one situated either in the woods or in some park large enough to be a satisfactory imitation… In New York, so far, there has been no such school camp, but at the present time twenty classrooms are being remodeled so that they may be used for open air classes, while on the famous out-of-commission ferryboats anchored off hospital piers there have been ungraded schools for some time. The remodeled classrooms consist of three walls and some shade. Except in rainy weather the children are as much outdoors as though they were on a veranda. The children who need it are given a rest hour and made to lie down and sleep in the middle of the day. It is a good idea, only a trifle less good than the really truly out-of-doors school.

OUT OF DOOR SCHOOLS ARE GROWING IN POPULARITY: Germany Adopted Them with Unusual Results and New York, Boston and Other Cities Are Experimenting Along the Same Lines (PDF)

From July 17, 1910