It is possible to implement. Testing students is not that difficult. After all, we have been examining students with all kinds of standardized test ever since formal education began. Similarly, we can know what teacher is involved in what result: the biology-teacher is relevant for biology, not French or arithmetic.  The economist Dale Ballou, in his 2001 article “Pay for performance in public and private schools” determined that the prevalence of merit-based pay in private schools demonstrates that it can be cost effectively implemented in complex institutional settings [1] .  [1] Ballou, “Pay for performance in public and private schools.” 2012.