A friend returned from Beijing recently and bought some books for Z, including a book on 三字经.
While Z had memorized and recited this in early K2, he had clean forgotten about it. As to whether he was taught the meaning of the verses, it was not clear if he had forgotten or not learned at all.
All thanks to this comprehensive book, I used it as a reference to explain the verses which were also supplemented with stories. He learned that we the parents were obligated to bring him up well, while his responsibilities were to pay attention, learn well and be an useful person in future.
Whether he remembered the teachings, at least it set a baseline and it was not my own idea to be so strict with him. It was ingrained in the Chinese culture.