Introduction to the History of America: Designed to Instruct American Youth in the Elements of the History of Their Own Country was published in 1787 and is generally recognized as the first American textbook. The author took passages from texts written for adults on American history and re-purposed them for young readers. So, in effect, young people have been learning about the country's history since the beginning. (My longer response to a similar question gets into the creation of history class.)

As an aside, while /r/AskHistorians establishes history as events prior to 20 years ago, American history curriculum authors don't necessarily follow that rule. I recently acquired a book called History's Greatest War, a pictorial narrative of World War I published in 1919, that was used in a high school history class in 1920. In addition, numerous state high school world history exit exams in the 1950's and 1960's asked questions about the Soviet Union that were written in the present tense and focused on current events. So, studying "history" in school isn't always and necessarily about long ago.