Background: Proof Blocks is a software tool that enables students to construct proofs by assembling prewritten lines and gives them automated feedback. Prior research has shown that students learn as much from an activity where they use Proof Blocks as where they write proofs. However, in both cases students first read a book chapter. Prior research was not able to differentiate between the learning gains achieved from reading versus proof practice. Purpose: This study aims to measure learning gains from reading a book chapter versus completing Proof Blocks. Methods: We conducted a randomized controlled trial with three experimental groups: one that only read a book chapter, one that only completed Proof Blocks, and one that did both. Findings: The group that completed only Proof Blocks had the smallest learning gains. The group that read the book chapter and completed the Proof Blocks activity performed marginally better than students who only read the book chapter, but it is not clear if the source of this improvement was the Proof Blocks or just exposure to more examples.