## Monday, 31 October 2011

### #9

Dr Lagina’s Math tutorial

√24/√3 = √(24/3) = √8

= √(4.2) = √4√2 = 2√2

√(81/25) = √81/√25 = 9/5

MOZ

Detention
Bramm S
Blake F
Morty
Hailey Y
Jordan A
Kara B

Mathematics – A-level standard.

These are some good examples of operations with surds, using the rules for both multiplication (n√(a.b) = n√a.n√b) and division (n√(a/b) = n√a/n√b). All the working is correct. The sloppy square root sign in the second example extending over the equals sign could be confusing, and handwriting in general isn’t great, but is legible.

Unfortunately, despite this good academic work, Dr Lagina is entirely unsuited to a career in education due to his surname. It would be no use trying to insist on a different pronunciation such as La-GHEE-na as students of any age will still make cruel remarks – it is little wonder that his detention list is so long. It is a shame that no careers officer ever tried to dissuade him from his current employment path, though he is still young enough to change his vocation. It is either that or change his name: even a teacher should be able to afford the £33 fee for a Deed Poll, though perhaps he has already changed it from something even more embarrassing, like Dr Lesticle, Dr Lyphilis or Nick Clegg.

There are a couple of other points to make. Firstly, a different hand has scrawled MOZ on the blackboard. According to Wilson and Kelling’s broken windows theory, a disordered environment signals a place where people do as they please and get away with it without being detected. Like the New York City Transit Authority removing graffiti from their trains leading to a sudden and significant drop in petty and serious crime, this should have been wiped off before the lesson began in a zero-tolerance approach. Not restoring a disordered environment early means that classroom discipline will only deteriorate, a fact surely worsened when one’s surname rhymes with a part of the female genitals. Whether Moz is the Morty who appears on the detention list, or just a deranged Morrissey fan is not clear.

Secondly, the appearance of Bramm S on the detention list raises the questions of how many students with this unusual name there are in this class that they need to be differentiated by their surnames, and whether this is a class consisting entirely of Gothic novelists, though there is no sign of Mary S or Edgar A P, and the works of Jordan A and Kara B must have been sadly lost to the world of literature.

8/10 – Good work, though loses a mark for ‘math’. And remember that sticks and stones may break your bones, but being called Dr Vagina every day of your working life will never hurt you. Though it may cause a career-ending nervous breakdown.

(Many thanks to Wim for sending this picture in.)

## Saturday, 15 October 2011

### Break Time!

Just to say that there will be a short break from lessons whilst we at Blackboards in Porn Towers stop looking at pornography for long enough to move to bigger premises. In the meantime, please do browse the archives.

Thank you to everyone for your comments and for sending in so many great images of blackboards in porn. We have been deluged with a shedload* of pornography, but hope to get through the backlog and posting reports again soon. It's a tough job, but somebody has to do it.

(* The SI unit of pornography)

## Thursday, 13 October 2011

### #8

- ½ beat
- 1 beat
- 2 beats

Music – introductory level

The treble clefs have been beautifully drawn, but there is no hiding some fundamental errors on this blackboard.

Firstly, the time signature is written as both ‘4/4’ and ‘c’. This is tautologous as ‘c’ means common time (4/4), so just one of these will do. Also, there is no need to put the time signature on every line unless it has changed, and there are definitely no mixed meters in Mary Had a Little Lamb.

There is a good attempt at an explanation of the different lengths of notes, though there are actually no quavers in this particular piece, so the teacher might be introducing the concept too early. The dotted minim might not be necessary either, and it is unclear what the minim with a quaver flag is meant to be. The teacher should also draw a semibreve for the last note ('snow').

The biggest error, however, is that each stave has only four lines instead of five. This would make it very difficult for the students to know which notes to play. Reading from the bottom, the first notes would be B A G A | B B B, which sounds correct. But reading from the top, the notes would be D C B C | D D D, which sounds wrong as there is only a semitone between the second and third notes. Imagine if half the class were playing one version and the other half the other – it would sound terrible and the class’s confidence might be badly affected if they felt they couldn’t master even this simple melody. (To be honest, when teaching this level of music it inevitably sounds awful when played tutti, so the teacher really isn’t doing his ears any favours here.)

An experienced musician would see that the positioning of the treble clef tells us which line is G (hence its alternative name of the G-clef), but it is unlikely that students of this level would know that. After adding the missing line to the top of the stave, the tune itself is basically correct, though usually the last two notes of bar four go up (to D in this case). The fact that the last note is a G helps to indicate that this version is in the key of G so needs a # sign on the F line just after the treble clef.

A good mnemonic for remembering the notes on the treble clef is, reading from the bottom line, Every Good Boy Deserves Football. Or, perhaps in the case of this classroom, Flagellation.

5/10 A good effort, marred by a silly error.

(Many thanks to Lucy for sending this picture in.)

## Monday, 10 October 2011

### #7

1. S=0 A=0
2. S=1/4 A=1/16
3. S=1/2 A=1/4
4. S=1 A=1
5. S=2 A=4
6. S=3 A=9

Mathematics
t p
m
n
3/4 02/5
100=S=A
A
S 42/A9

Mathematics - year 8 level

This sets out to be a good illustration of the function more commonly expressed as y=x2. (Why the teacher has chosen A and S is unclear; these are sometimes used in lower case form as acceleration and distance respectively, but the relationship between them would not then be physically correct.) The important points (S=0, S=1, two points where S<1 and two points where S>1) have been well chosen to illustrate this function, though it would have been useful to have included some more points where S<0 to show what happens when squaring a negative number.

The graph has then been plotted, but sadly this is where the lesson begins to falter. Firstly, axes on the graph should be labelled with 'S' (horizontal) and 'A' (vertical). And the graph that has actually been plotted seems to be more like:
1. S=0 A=4
2. S=4 A=8
3. S=6 A=15

The graph is roughly the correct shape, but is not positioned correctly: it clearly intersects with the vertical axis at A=4. Even allowing for other drawing errors, this is a function more like A=bS2+4. It would also have been useful to extend the graph to S<0.

What is going on on the right-hand blackboard is less clear. There is a drawing of a trapezium, and also the equation 100=S=A, which is hopefully not meant to be related to the function A=S2.

Finally, the teacher should make sure that her students keep their focus on their work. She only has three students, so can't complain too much about the pupil-teacher ratio. The teacher is giving all her attention to the lone male student, allowing the two female students to talk to each other, thus reinforcing gender stereotypes of women in maths, despite being female herself. Sadly, it is this kind of attitude which leads to the 'Math class is tough' talking Barbie and low numbers of women choosing to study maths in further and higher education.

5/10 Shows some promise

(Many thanks to Chris for sending this picture in. Please keep them coming, folks.)