A school district will use grade 1-5 students at one elementary school to study whether a new reading program can produce better reading comprehension scores. Half of the students will continue with the current program, and half will receive instruction with the new program. Which is the most appropriate design?
A) Completely randomized, randomly assigning students to reading programs
B) Randomized blocks, blocked by reading program
C) Randomized blocks, blocked by gender
D) Randomized blocks, blocked by grade level
E) Randomized blocks, blocked by both grade level and gender