How, and what is the best way of grading students on duolingo? I will appreciate your input. Thank you for your interest.
Duolingo is a very good teaching tool, but I don't think it has good assessment tools for teachers. The only thing the students could use is the Progress Quiz, which can be bought from the lingot store, but that relies on the students having enough lingots. Unfortunately it isn't yet possible to assign the progress quiz through the Schools interface, or to see the results your students achieve.
I give students extra credit points based on their XP level. I have given one extra credit point for each 100 xp points. I'll check their point level each quarter...so after the first quarter they are on their own and are definitely at different levels. (What's new!)