Effects of assessment on curriculum and instruction were studied in an investigation that considered local educators' reactions to statewide minimum competency testing, the instructional effects of implementing these tests, and variations within each state. The two states examined were Pennsylvania, a low-stakes situation with relatively minor consequences for the student, and Maryland, a high-stakes situation where high school graduation depends on passing the tests. Pennsylvania students were tested in grades 3, 5, and 8, while Maryland students were tested beginning in grade 9. Fieldwork was conducted in six sites in each state, and over 250 local educators and students were interviewed. A survey completed by 277 of 501 Pennsylvania districts and 23 of 24 Maryland districts provided additional information. The impact of the testing program was far greater in the high-stakes situation, and this impact seemed positive as long as the districts were not under too much pressure. Both positive and negative consequences are discussed. Five tables present study findings. (Contains 14 references.) (SLD)