The slaveholding colonies and states of the American South are one such example, where the slaveholding class used illiteracy as a way to make it easier to control the enslaved population.
An act from South Carolina of 1740 made it a fineable offense to teach slaves to read or write:
Whereas, the having slaves taught to write, or suffering them to be
employed in writing, may be attended with great inconveniences; Be it
enacted, that all and every person and persons whatsoever, who shall
hereafter teach or cause any slave or slaves to be taught to write, or
shall use or employ any slave as a scribe, in any manner of writing
whatsoever, hereafter taught to write, every such person or persons
shall, for every such offense, forfeit the sum of one hundred pounds,
Similarly, the Virginia Revised Act of 1819 threatened with up to twenty lashes any slave who tried to learn to read or write:
That all meetings or assemblages of slaves, or free negroes or
mulattoes mixing and associating with such slaves at any meeting-house
or houses, &c., in the night; or at any SCHOOL OR SCHOOLS for teaching
them READING OR WRITING, either in the day or night, under whatsoever
pretext, shall be deemed and considered an UNLAWFUL ASSEMBLY; and any
justice of a county, &c., wherein such assemblage shall be, either
from his own knowledge or the information of others, of such unlawful
assemblage, &c., may issue his warrant, directed to any sworn officer
or officers, authorizing him or them to enter the house or houses
where such unlawful assemblages, &c., may be, for the purpose of
apprehending or dispersing such slaves, and to inflict corporal
punishment on the offender or offenders, at the discretion of any
justice of the peace, not exceeding twenty lashes.
Nat Turner's revolt of 1831 -- and the spread of abolitionist literature -- led to a rash of new or strengthened anti-literacy laws in the South, in states including Delaware, Georgia, North Carolina, Alabama, and Mississippi. Related to this fear of abolitionist literature, in 1835 several states also made it illegal for the postal service to deliver this literature.
Keep in mind that on the eve of the Civil War, the enslaved percentage of the population was as high as 57%. This makes southern anti-literacy laws a clear example of a ruling class using illiteracy to make it harder for a more numerous, enslaved class to coordinate resistance or even question the status quo.
Former slaves and northern Republicans recognized that literacy and public education would be needed if former slaves were to defend their rights in the post-war South. This is why establishing public education in the South was a major goal for Republicans during Reconstruction. Southern legislatures resisted funding those schools that served black Southerners when possible.