K12 Teaches Estimation

Posted on April 1, 2014

My daughter attends k12 (the local branch) which is an online school. Since she’s only in kindergarten at this point, it’s a time intensive activity for both of us. It differs from home schooling only insofar as the curriculum is set by k12 rather than being more free form. So we’re required to teach estimation before the kids can add numbers up to 100.

Therein lies the problem. Here are the fundamental flaws (in my view) of trying to teach estimation this early.

Where Did the Jelly Beans Go?

Remember the big jar of candy that you needed to estimate to win? That was a good first step to teaching estimation – you can’t see all of it, but you can estimate. Unfortunately, in a near-home schooling situation, it’s not as feasible, since the competition is nil.

No Mental Arithmetic Background

First, to see the beauty of estimation, one must first be able to calculate with round numbers in ones head better than with exact numbers. Since there is no emphasis on adding and subtracting round numbers (by 5s or at least 10s) there is no difference in the time it takes to calculate the exact answer rather than using estimation.

For example, I found that my daughter would invariably have finished counting before she was ready to make an “estimate”. I can’t really fault her for giving the correct answer, especially since she performed all the math in her head, but it did not give her a sense of what estimation’s value was.

Estimating Numbers Under 20

This was an actual unit name. Yes, “estimating” numbers under 20. The same amounts that my daughter is already adding and subtracting in her head without use of any props. There is no value in estimating what can be quickly calculated, and it was frustrating to both of us trying to come to the same conclusion.

Cumulative Estimation Error

One of the big focuses was to estimate values, and then use the values to perform calculation. This is fine for really big numbers, but when you’re estimating values under 20, it leads to a lot of confusion…

For instance, 17 − 9 would be part-wise estimated into the expression 15 − 10. So the answer is ‘about 5’, right? But when she calculates it out, she’s reporting 8, which is supposed to be ‘about 10’. And I’m supposed to mark her ‘about 10’ as wrong? Even though 8 is be considered to be ‘about 10’ in every other case? Ridiculous, confusing, and frustrating.

Teach the Concept, Not the Arithmetic

We ended up fudging our way through the two week’s worth of lessons dedicated to estimation. I tried to show her every way I could how estimations are used in practice. We even drew out benchmarks (real marks on a bench) so that she could see how estimations can make sense. I think I managed to get many of the salient points across, but the entire fiasco left us both with a bad taste.