The first conflict in Tess is between her two languages: the thick, west country dialect her parents speak and the much more standard English she is taught to speak at school. Hardy later tells us that when Tess is with her mother, the Jacobean (the period during the rule of James I) and Victorian ages stand side by side, representing this gap as a time span of over 200 years.
The standardised school system was introduced during the Victorian era. Although education for all children wasn't mandatory until 1871, by the mid-nineteenth century the Church of England had set up a series of National Schools where reading, writing and arithmetic were taught. In out of the way places such as Marlott, these would typically have been overseen by one teacher, with children of all ages learning together in one room.
As you can hear from this 1930s recording of a Dorset accent, thick west country accents could be quite hard for outsiders to understand: