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# Math was Wrong

The difference between 6th and 7th grade was 17, not 27. As such, the growth curve is 24, followed by 17, for an average of 20.5.

I didn't understand the calculation ?. How can you predict how many 6th graders will there be next year?

I just saw this video and have NO IDEA how he got to the number of 6th graders from next year. Also, why was it in the lesson if it wasn't calculated with SQL? It threw me off.

Having said that, I am enjoying the videos and learning plenty :)

STAFF

D'oh! Thanks for keeping me honest! It looks like we'll be making an update to this video in the near future :)

Mistakes happen, nbd. I'm really enjoying the video series so far. Keep up the good work Ben!

Four years later...

I don't think making mistakes in a video is a big issue, but when you do it repeatedly like in the previous video while trying to select the right columns it makes the example really hard to follow.

So I must have missed something because the first thing I thought of was this:

```SELECT COUNT(*), GRADE FROM STUDENTS GROUP BY GRADE;
```

But it was giving me a count of all students and so that led me to do UNIONS

```SELECT COUNT(*) AS student_count, GRADE FROM STUDENTS WHERE GRADE = 8
UNION