Tonks | Cassiopeia
I can sympathise. In my case it was being told that I'd be good at everything just because I was a Black. I ended up starting my first year in January rather than September, and so spent most of it near the bottom of the class and trying to catch up enough that I wouldn't be made to repeat the year. I think Dippet was actually disappointed when I passed. He wasn't the most inspiring of headmasters.
Yes, it's so very important to be able to protect yourself - although knowing the right way to protect others can be difficult sometimes. Justice isn't always straightforward.
Arcturus loves Transfiguration, too! They put him in an advanced class at school here, I've heard. Now, does that mean that the food is actually decent, none of those awful flobberworm fritters they used to give us?