Closer to 24 months for many but, many of these kids don't actually comprehend what they are doing. My daughter in K and 1st grade(4 to 6) had many friends that could rattle off 1 to 100 and do simple math. Yet if you asked them to move five spaces on a game board, or pick up ten pencils. They couldn't do it. They weren't making the connection. They could pick up a book and read you the words, but if you asked them what they just read, they had no idea. That young of a child that con as you say and then tell you about what they just read, or hand you 7 beans. Would be the exception. If you test, use different materials then what they already know.