Would you be shocked by this teacher's understanding of maths?

[KOKOagainandagain]

A teacher is DS2's school recently wrote:

"96th percentile to 100th percentile = an average child performing at expected level. To be significantly above you would expect a child to be above 110th percentile"

What??? 110th percentile !!! Above 110th percentile?!?! How is that possible???

God knows what nonsense she is teaching her class.

I'm pretty confident there is no such thing and that this is a pile of bollocks. Why do teachers expect parents to swallow obvious bullshit? and that any parent that asks politely for clarification (nothing so harsh as pointing out actual impossibility) has an attitude problem

jobspotting.com/wp-content/uploads/2015/09/110-percent.jpg

Remember the part in King Of the Hill. The Hill family on the way to Bobby's baseball game.

Hank Hill: So, are you ready to kick some Wildcat butt, Bobby?
Bobby Hill: Okay.
Peggy Hill: Nah, don't you worry, son. You just do your best.
Hank Hill: Don't listen to her, Bobby. If you wanna win, you're gonna have to do better than your best.
Bobby Hill: How do I do that?
Hank Hill: You gotta give a hundred and ten percent. That's what'll give you that winnin' edge.
Bobby Hill: But what if the Wildcats give a hundred and ten percent, too?
Hank Hill: Well, then you gotta try even harder.
Peggy Hill: How about if Bobby gave a hundred and twelve percent?
Hank Hill: Ahm ... sure, that'd work.
Bobby Hill: Or maybe a hundred and thirteen?
Hank Hill: [Annoyed] Yeah, yeah, that's even better.
Peggy Hill: No, uh, I don't know. Thirteen is a very unlucky number.
Hank Hill: Look, we're not talking about thirteen. We're talking about a hundred and thirteen, and even ... uh ... okay, give a hundred and twelve, what's the difference? Look, Bobby. Just do your best, okay?

[Finola1step]

You're correct. But I suspect that the teacher was referring to age standardised scoring. Now that schools are assessing without levels, age standardised scoring is becoming popular again. If that's the case, then yes, a score of 100 is expected. Anything above 110 might be considered as a child exceeding expectations for their age.

So I think its the vocabulary that is muddled.

[mrsmilktray]

She means standardised scores doesn't she?

[MovemberSucks]

Is she confusing it with IQ points, where the average is considered to be 100?

[SoupDragon]

It sounds ridiculous.

However, looking at the growth charts in the Red Books, what percentile is a child who is over the 100th percentile??

[KOKOagainandagain]

I would like to think that she is merely confused but she has used the word 'percentile' three times.

There seems to be a basic misunderstanding of what statistics actually mean and the need to be precise in the use of language.

As it stands, it does not make sense.

Would you not expect a teacher to notice what what they have written cannot possibly be the case?

We can assume the teacher was actually referring to standardised scores. A standard score is a measurement of achievement.

Percentile rank is a different issue and 96th to 100th percentile is not 'average' (commonly SS would be above 126)

[Happymummy007]

I think this might be called The Cambridge System? (I might have got the wrong name - apologies if so). Our school uses them. It's been explained to me thus: the average intelligence of the UK population is 100. Anything above that is, obviously, above average. Some schools (ours included) carry out certain tests (verbal reasoning, mental arithmetic, spelling etc) and when the child is marked, they need to score above average marks. This is worked out as, say, 5 out of 10 would be the average mark achieved, but 6 out of 10 or higher means that you have above intelligence - and this mark is then translated into an IQ score. Our school aims at children scoring 110 or more, but I know of other schools that aim at 115 or even higher. I'm not surprised you were confused - the word "percentile" doesn't help at all.

[caroldecker]

Happy I don't think she was confused, I think she was pointing out the teacher's blatant ignorance of not understanding the differences between standardised scores and percentiles.
The world percentile is fundamentally wrong and marks the teacher out as a fuckwit less than secure in their knowledge.

[KOKOagainandagain]

A standard score of 138 is 99th percentile.

Scores above 138 (only up to 150 on standard assessment such as WISC) are converted to percentile ranks between 99.5 and 99.9). At a population level standard distribution is always between 99.9 so statistically speaking, no-one is ever >100%.

[KOKOagainandagain]

This is why I suspect more than ignorance and confusion on the part of the teacher. DS2 has been assessed by the LA EP and found to have NVR and VR abilities on the 99.3 and 98th percentile.

The comment above was written as a refutation of DS2 'really' being above average ability. This meant that the the EP was wrong to claim statistically significant underachievement (using WIAT).

[mrz]

She's talking about "scale scores" which will be the measure used in end of key stage national curriculum tests (SATs) and yes it shows poor understanding of percentile ranks.

[mrz]

Scaled scores
The move to scaled scores was announced as part of the previous government’s response to the consultation on reforming assessment and accountability for primary schools.

Scaled scores are used all over the world. They help test results to be reported consistently from one year to the next. We design national curriculum tests to be as similar as possible year on year, but slight differences in difficulty will occur between years. Scaled scores maintain their meaning over time so that two pupils achieving the same scaled score on two different tests will have demonstrated the same attainment. For example, on our scale 100 will always represent the ‘national standard’. However, due to the small differences in difficulty between tests, the ‘raw score’ (ie the total number of correct responses) that equates to 100 might be different (though similar) each year.

We can’t give full information about what the scale will look like yet. We need to wait until pupils have taken the tests and the tests have been marked before we can set the national standard and the rest of the scale. We can’t set the scale in advance; this cohort is the first that has reached the end of key stage 2 having studied sufficient content from the new national curriculum. If we were to set the scale using data from pupils that had studied the old national curriculum, it is likely it would be incorrect.

We do know the scale will have a lower end point below 100 and an upper end point above 100. Once we have set the national standard we will use a statistical technique called ‘scaling’ to transform the raw score into a scaled score. We will publish this after the first tests have been administered.

The standards underpinning the scale will be maintained as long as there is no large-scale change to what the tests cover. Once the national standard has been set in summer 2016, we will maintain the standard in subsequent years by using a process known as ‘test equating’. When we trial future tests in schools, we also administer a separate ‘anchor test’. This test remains the same over time. It allows us to link scores from one test to another to ensure standards are maintained.