Over the summer, I've been working with the little Oni on her math skills. Her teacher 'taught to the test', and those tests (as I said earlier) were 'multiple guess'. It's really struck Mr. Oniya and myself how much of a disservice that was to her, when we see her getting frustrated because the idea of working the problem to the very end hasn't occurred to her. Example: Given a set of ten numbers, determine which are prime, and which aren't. For the composite numbers, write down the prime factorization.

She encounters '49'. The text has given handy divisibility tests for 2, 3, and 5. She knows her times tables up to the 12s. She still only bothered to check 2, 3, and 5, and wrote down that 49 was 'prime'. Later on, there was another 'divide by 7' number, that she also marked incorrectly as prime. I fully admit that the final number, 289, was a challenge, but by that point, she should have grasped the idea of trying and discarding numbers.