Alas, I'm not sure what the author of the tweet had in mind here as 1920 wasn't, as far as I know, an especially meaningful year for formal education. 1820-ish, on the other hand, marked the start of the feminization of the teaching profession and the rise of common schools in America. He might be referring to the work of progressive educators like Dewey or but the rest of his thread leads me to suspect he's referring to the emergence of psychometrics (assessment design) and learning sciences as a branch of psychology. Especially where he says, rather emphatically:
WE.
DON'T.
KNOW.
HOW.
PEOPLE.
LEARN.
There are a few things going on here that worth addressing. First, all of his examples in his thread are based on his experiences in Texas. It cannot be stressed enough that what happens in Texas is unique to Texas. In this answer to a question about history education, I use Texas and NYS as examples of how different states deal with standards. Which is to say, nothing he says about Texas standards applies to New York State. Especially when it comes to the role of school boards (I get into that in an answer here.)
Meanwhile, there is an argument to be made - and there are education historians who make it - that the American public education system is actually only 46 years old. The Individuals with Disabilities Education Act was first passed in 1975 - removing the excuses school districts had for not enrolling children with disabilities. However, one could argue that really didn't happen until court cases like Plyler v. Doe (1982) that ruled districts are required to educate immigrant children, regardless of their immigration status. Or the McKinney-Vento Act (1987) that requires districts to educate an unhoused or home-insecure child within its boundaries. So, in that case, the modern American education system is basically a millennial.
But as I said earlier, I think he's actually talking about the learning sciences and our understanding of how learning works. Alas, he's being a tad hyperbolic - and I would offer, a tad unfair to those who study learning, especially when he compares it to astrology. Saying "we don't know about people learn" is a bit like saying, "we don't know how black holes work." Because we do. But not really?
In other words, we have a general understanding of how people learn. And we did back in 1820 and 1920. The most common form of assessment - which is to say, deliberate moves by adults to collect evidence of student learning - was known as recitation. From an older answer:
A student would listen to a more knowledgeable person or recognized expert (typically a person from the group that held power - i.e. men) talk, discuss or practice what was said, and repeat (or recite) back when asked. There were generally two types of recitations. The more knowledgeable person would expect the learner to repeat back verbatim what they heard (what we think of as memorization) or repeat back and comment on what was learned by adding a personal opinion. For men like Socrates and Aristotle, the nature of this interaction was less about knowledge transmission and more about helping the student uncover "true" knowledge. This meant that, yes, Aristotle quizzed Alexander in the way we think of the word today; Aristotle would ask Alexander a question based on something the boy had studied and would respond based on the nature of his response.
Recitation is still used in the modern era - though we describe it differently and have a more robust vocabulary to distinguish what the student or teacher is doing (pop quiz, discussion, memorization) - because it works. While it's true we now understand the specifics better than we did in the 1820s or 1920s - we know about dendrites, neurons, chunking, short and long-term memory - this doesn't mean educators in the past were just doing any old thing without giving thought to what they were doing. They knew back then that sometimes we learn things because we hear, read, or see it and it connects to our background knowledge and becomes part of our long-term memory. Other times, we have to repeat it or develop a mnemonic to get it to "stick." (I'm simplifying learning sciences a whole bunch - I recommend Daniel Willingham's books or Pooja K. Agarwal and Patrice M. Bain's book which comes at the topic from the teaching side.)
At the same time, educators in the past knew that children needed to do things in order to learn. Progressive educators didn't invite the idea of "active" or "participatory" learning. The entire model of apprenticeship in the crafts and trades is based on our understanding of how people learn through observation and coaching. Those who wrote about "hands-on" learning before the modern era weren't outliers - they were run-of-the-middle educators. Teacher preparation programs in the 1800s routinely included outdoor learning or how to handle students doing group or collaborative work (not in the same way we think of it today, but more "here's what you can do when you have one primer and 20 children.") We can also see the presence of participatory learning in surveys of the era. In this answer, I get more into the history of history class and one of the documents I reference is the Committee of Ten reports. It's often cited as one of the foundational documents of American education and from it, we can get a sense of the prevailing mood around education in the late 1800s. From the Natural Science report. (emphasis is theirs)
The study, to be of much value, must consist largely of laboratory work, actual work, by the pupils, with the plants or animals. This cannot be too strongly emphasized.
To be sure, there's a whole bunch of formerly common practice that's no longer done and fads in education are a whole other topic. Corporal punishment has mostly been phased out - we know children don't learn what we want them to learn when adults use physical violence against them. And yes, our understanding of what school should be is constantly changing. But it is misleading to suggest we don't know how children learn or that education is only 100 years old.
