Hand drawing

Every time I also liked drawing with pencil, chalk or pen because it is amazing what you can create from simple lines. I guess if you draw you can't cheat thus I don't like to use ruler or any aids to drawing so I only use my hand drawing skill. I know it is not on the professional level but I do my best all the time. I like improving my skills as a result I have been learning at an art school in Szeged for a year and a half.
So, I am interested in your opinion about my draws.
Here the first one is:

There are lots of simple things in the classroom and I guess, it would have been easier with ruler :)