What makes teachers work more

. . . [L]evels of some non-pecuniary incentives—teachers being able to choose their teaching method and having a school PTA [Parent-Teacher Association] —increase the probability that teachers offer tutoring lessons by between 11 and 34 percent. Allowing teachers to develop their own teaching materials induces them to work approximately 3 hours more per week preparing for classes, presumably time spent developing the materials . . . (P.17).

That is from this paper by Hai-Anh Dang & Elizabeth King.