Abstract:  Student achievement of skills is critical to raising living standards even in Tanzania, where right now less than 20 percent of high school students are passing their national promotional mathematics test.  In order to understand whether this level of achievement is because (1) students are disinterested in the curriculum; (2) lost and unable to follow the curriculum; or (3) both of the above; I conduct a field experiment with 6,201 students, 170 high schools, and a three-year follow-up, providing students with (1) money pegged to math test scores, (2) technologies to ease the effort costs of learning, or (3) both of the above.  I find that money or technologies alone make limited impact on test scores, while both together produce a large, complementary effect (0.3σ), especially on the scores of students below the top 20 percent.  I estimate a model of students who recognize the benefits and costs of learning, including certain fixed costs of even trying to study that they only incur if there are sufficiently large benefits.  I use the model to value test scores and promotion; compute welfare implications of the interventions; and simulate counterfactual outcomes from lowering the promotional cutoff---a low-cost policy option that would offer more students a realistic chance of promotion and, therefore, a higher expected return from marginal effort.  The model suggests that both providing the experimental inputs and incentivizing the students by doubling their chances of promotion in mathematics will induce a modest but meaningful endogenous response of student knowledge, by reducing the share of students who are giving up on learning at the margin from 79 percent to 52 percent.  By explaining treatment complementarities, the proposed model extends a standard model of classroom learning from the previous literature to reflect a higher degree of realism about developing community contexts.