For x by: pelo(s), pela(s)

Pensei em:

'I can see from the looks of your tennis shoes that clearly you don't respect/follow the school's rules'.

Mas vamos aguardar outras sugestões.

And also: Your ragged shoes/sneaker shoes speak volumes about your (dis)regard for the school rules!

From your ragged shoes/sneakers I take it that you don´t have (any) regard for the school rules?
It works as an statement here, but be aware that it´s not everyone that like statements-turned-question - I mean - authors, etc.
Plus, somehow the student couldn´t understand, or be beyond his grasp, and he/she could also be sarcastic/ironic or try his/her luck and answer "no, you can take it that I do have, Sir/Madam."

PPAULO escreveu:And also: Your ragged shoes/sneaker shoes speak volumes about your (dis)regard for the school rules!

From your ragged shoes/sneakers I take it that you don´t have (any) regard for the school rules?
It works as an statement here, but be aware that it´s not everyone that like statements-turned-question - I mean - authors, etc.
Plus, somehow the student couldn´t understand, or be beyond his grasp, and he/she could also be sarcastic/ironic or try his/her luck and answer "no, you can take it that I do have, Sir/Madam."

Obrigado! Mas quando se usa o For/By/From em uma frase com esse sentido de Pelo (a)/Pelos (a) ?

One possibility would be "by the state of your shoes, I take it that..."

One way to get acquainted with the ways of its usage is to type part of the sentence and search on the Linguee site (or others as well).
Example: if you search with "respeito pelas regras da" and crawling into some of the "hits" you´ll see that a pattern will emerge it will be "respect for the rules..."
Same happens with "disregard for the rules..." and so on.
You can use Wordreference too, along with others sites. And the entries in dictionaries also can be a source of grammar notes.
Then if any doubts arise, feel free to come and bring it to us.

From is essentially in the sense of "origin/starting point" etc. You can see some other cases on Wordreference, for instance.
In our case "from" is the starting point where we can make the subsequent deduction, that of "disregard for the rules...".

http://www.wordreference.com/enpt/from