For teachers: how to read a child's soroban mistakes

For teachers who want to know why a student went wrong, not just that they did.

Read a wrong answer as a wrong bead movement, not as "a calculation error". Four types cover almost everything: 5-complement, 10-complement (carrying and borrowing), column shift, and reading or copying. A tick-and-cross score cannot show the type, so have the child redo one wrong problem on the beads in front of you. When the same type appears three times, give five problems of that type only.

The four types and how to tell them apart

Procedure: redo one, three-times rule

1. Have the child redo one wrong problem on the beads while you watch. Where the hand hesitates is the type. The score alone cannot tell you.
2. Same type three times means a habit. Once is a lapse of attention. Three times, give five problems of that type only.
3. Recheck a week later with three problems of the type. If it is still there, drop one level and increase the share of problems where that type occurs.

What not to look at

• Speed. Fast children skip 5-complements. Accuracy first.
• The total score. An 80% whose errors are all "carry" needs one fix. An 80% with one error of each type is on too high a level.
• "Careless". Filed as careless, nothing gets fixed. Every error is one of the four.

Recording

A ready-made version is the free printable mistake observation sheet: one page, 20 students, codes and what each looks like in the answer.

A one-page grid, students down the side and the four types across, with a tally mark per error per lesson. Paper is enough. After a month the pattern is obvious: this child is all carrying, that child is all copying, and the first three homework problems can be chosen accordingly. Beyond about twenty students the tallying stops keeping up; a tool that draws the wrong bead movement, classifies it by type and tracks whether each habit is fading (Soroban Kingdom does this) can hold the record instead.

Mental arithmetic errors are a fifth case

In anzan there is an extra failure: the image faded. If a 3-digit, 5-term mental sum goes wrong at the fourth term every time, the image is not holding long enough. Reduce digits or terms by one; it is not a bead-movement error.

One condition of good soroban learning is that mistakes are visible by type. Watch types fall, not scores rise.

Frequently asked questions

Accuracy or speed first?

Accuracy. Promote at 90% correct; measure speed only against the exam time limit before an exam. Speed first produces the skipped-5-complement habit.

I have too many students to watch each one redo a problem

Use the first ten minutes: each child redoes one wrong problem from last time with a neighbour watching. You watch only the hands that stop. If that is still not enough, let a tool record the bead movements and look only at the "needs attention" list.

How do I explain an error type to parents?

By type, not as "careless mistakes": "She forgets to add the carry bead. This week we are fixing only that." The parent does not need to teach anything and the child is not blamed.