Based on Zee Edgell's book Beka Lamb, we know that the title character Beka is a Creole girl living in Belize, a Central American nation bordered by the Caribbean Sea.
In South America and the Caribbean, the term Creole is used to describe the descendants of white Europeans and African or Native American slaves. In the 1950s, Creoles were actually found in all three of the social class divisions. There were the elite, landowning Creoles, who even owned slaves when slavery was still legal. There were also the middle-class Creoles, and in fact many of the political leaders of the 1950s were Catholic-educated middle-class Creole. Finally, there were also the lower-class Creoles.
We know that Beka's family is continuing to pay for her Catholic education, and it was and still is very rare for lower-class Belizeans to continue their education past primary school. Therefore, Beka's education alone places her in the middle-class sector; however, the same is not true for her friend Toycie. Toycie also attends Beka's school but at a tremendous cost to her family, who want to help Toycie rise above her poverty. Aside from being able to place Beka in the middle class due to her education, we can also place in her the middle class due to her father's job. We know Bill Lamb has a white-collar job with a firm owned by Mr. Blanco. Therefore, Beka may even be more upper middle class than just middle class.