It all depends on indivisual person and his/her ability than being a graduate of such and such TOP ranked or LOW ranked school. Let me give my own example here if you guys don't find it boaring to read.

 I went to a school remote part of Nepal where finding a science/math teacher was a dream. The headmaster used to go to neighbouring indian city each year at the begining of the session and grab some indian(with fake Bsc certificate) who used to be driving Riksaw there, bring him as a science/math teacher. No nepali or English he could speak. Teach for sometime and learn some nepali language and go to another school which would give better salary (remember that the headmaster et all used to give less than half of the regular salary to those Bsc-ers). I passed slc with 51%. Just to tell you that ,due to lack of teacher, there was no OPTIONAL MATH subject in that school. (When I was doiong my Isc some of my class mates, who were from city area and pass out of boarding schools with high score, used to make fun of me saying 'wa wa..wa... Optional math napadhi pani Science padhne bhako'. Guess what they failed the ISC in the end).

Then I went to a nearby college for ISc where again we didn't have math teacher. The administration brought a math teacher from India, who could not speak Nepali/English.  sometime he used to walk out of the class room not even  speaking a single word, just doing math on the board. One day, as usual he was doing a problem in algebra or something where there would be no chance of showing up trig functions like: sin, cos etc. A student from taplejung (who would not speak/understand hindi) asked a question: Sir tyo KASari aayou? Guess what the teacher answered? 'Aare bhai yaha to COS hi nahi he'. The teacher only caught the word COS from the word KASARI!!!!!!!!!! Anyway, long story I passed Isc with 52%.

Then moved to Ktm, joined ASCOL for BSC, Passed it with 56%. Joined Kirtipur campus, finished masters in one of the Science areas with 81%.

Joined for Phd in one of the North American University. Finished it and now teaching in one of the reputable North American institutions.

My whole point here is: the OPPORTUNITY and PASSION are the key things to success. It does not matter WHERE you go for your studies.