$5,000 per year to start.  4 proficiency tests during each year.  Each percent below perfect takes away 1% of the remaining money.  Anything below 70% OVERALL proficiency is failing and you don't get any money for failing.  So, in theory, a student who got 70% for 3 tests and 71% for one test would get $5,000 x 70% x 70 x 70% x 71% or $852.  That's 17% of what they could have earned.

A student who received 50%, 70%, 80%, 90% would receive $1,260.  More than the student who makes no effort to improve, but less than giving effort all the way through.

Real life incentive; real life penalty for being a slacker.