Analysing the Secoud and Planning the Third Lesson:
'A View Turn'
After having analysed the second lesson and the results from the post tests it became clear to the team that lesson 2 was not successful either. The post-test showed that the students performed better on tasks concerning subtraction especially to subtract a negative number from a positive number. Certainly the results increasedfrom 41% of correct answers on the pre-test to 76% on the post-test, but results from subtraction tasks with two negative number '(-5)-(-2)=', did not increase so much (from 41% to 65%). Since the lesson paid little attention to addition with negative numbers the increase in results concerning addition was small. So, having planned and conducted two lessons in the cycle without getting the outcome they had expected, they realised that there were still some critical aspects that remained to be discovered
Neither using a pattern (as in lesson 1) nor comparing pairs of numbers with the help of a number line (lesson2) seemed to give the students possibilities to learn what was intended. All aspects critical for learning this had not been brought out in these lessons. But still there were a few things in lesson 2 that they were satisfied with. The post-tests had shown better results for subtraction compared to lesson 1. The teachers considered what effect that 'negative difference' never appeared in the lesson may have had: "You never showed a negative difference between numbers. 5-1 should have been followed by 1-5," T3 said. "We had decided to try to avoid that. We felt that it would mess up things for them", T2, the teacher who had implemented the lesson, said. A long discussion about whether they should try to avoid or focus on expressions with a negative difference followed. Would it be confusing for the students or was it necessary to bring this up? Could the difference between '5-4=' 'and 4-5=' be a critical aspect (i.e., the law of commutativity is not valid for subtraction)? "You could start with 4-5= and discuss what happens in that case. With '5-4=' it will beone left, but with '4-5=' it will be one missing. That difference is understood by every little child," the researcher said. "Yes, and still we ignored that since we felt that we could not explain that," T1 replied.