It is following his adoption by his long-lost Aunt, Betsey Trotwood, that David is sent to a new and infinitely better school than the one he was sent to in London by the Murdstones. This event occurs in Chapter 16 of the novel and describes Dr. Strong, his new teacher, and how it takes him a while to adjust to being back into school life. However, he says that Dr. Strong is an excellent teacher and he soon settles back into learning. Note how the school itself is described:
The schoolroom was a pretty large hall, on the quietest side of the house, confronted by the stately stare of some half-dozen of the great urns, and commanding a peep of an old secluded garden belonging to the Doctor, where the peaches were ripening on the sunny south wall. There were two great aloes, in tubs, on the turf outside the windows; the broad hard leaves of which plant (looking as if they were made of painted tin) have ever since, by association, been symbolical to me of silence and retirement. About five-and-twenty boys were studiously engaged at their books when we went in, by they rose to give the Doctor good morning, and remained standing when they saw Mr. Wickfield and me.
Note the pleasant description of the hall. The peaches could be seen symbolically as the way that Dr. Strong's influence is able to "ripen" his students, and the aloes are likewise symbolic of the discipline of silence and study that Dr. Strong is able to instil into his charges. The boys are described as hard-working and respectful, which is yet again another indication of the good teaching skills of Dr. Strong.