The 'value-added' debacle
Leading mathematician debunks use of VAM
The L.A. Times is once again publishing the names of every teacher in the district next to a concocted "value-added score." The reputations and careers of thousands of teachers hang in the balance with the Times' use of a bogus formula they claim can distinguish good teachers from bad ones, who should get "merit pay"and who should lose their jobs.
In a scene out of the theater of the absurd, even Supt. John Deasy and other district leaders are protesting the Times' release of this data, claiming the district is using a different, competing formula from the one used by the Times. Here's Deasy' formula:
The L.A. Times is once again publishing the names of every teacher in the district next to a concocted "value-added score." The reputations and careers of thousands of teachers hang in the balance with the Times' use of a bogus formula they claim can distinguish good teachers from bad ones, who should get "merit pay"and who should lose their jobs.
y = Xβ + Zv + ε where β is a p-by-1 vector of fixed effects; X is an n-by-p matrix; v is a q-by-1 vector of random effects; Z is an n-by-q matrix; E(v) = 0, Var(v) = G; E(ε) = 0, Var(ε) = R; Cov(v,ε) = 0. V
