That's not correct. Un taco grande. El taco bueno. Un taco nuevo.
Adjective placement can be before or after, depending on the intended meaning. http://spanish.about.com/od/adjectives/a/adjective_placement.htm http://spanish.about.com/cs/grammar/a/whereadjective.htm
A retired teacher: I would always say "poor" student - nothing to do with money! - to indicate she does not do well in her studies - an academic judgement. A "bad" student would be one who cheats, steals classroom supplies, or deliberately disrupts the class - a moral judgement.
The Duolingo sentences are not mean to provide us with information to learn stuff, they exist to teach us Spanish, and that is all.
Nice things being said and not so nice things being said, makes no difference.We need to be able to read it all.
It is even important to understand someone when they are cussing us out. Duolingo does not provide that education. However, it is an important one to gain. It could help keep one from being harmed. Ignorance does have its drawbacks. Short comings. It is really stupid to remain stupid. Always. This applies to everything. There are no bad words to learn. This includes bad words.
Yep. That's why I dropped out of college and now I work a mindless menial labor manufacturing job that will probably be outsourced thanks to automation in about 5-10 years. Stay in school if you can afford it, kids, and seek out help the moment you feel like you're coming apart at the seams.