Since everyone in the control group and the test group applied to the VPK program and was randomly placed into either the test or control group, we have good r

Since everyone in the control group and the test group applied to the VPK program and was randomly placed into either the test or control group, we have good reason to think they have a similar background and needs... But maybe the kids who didn't get into the program then had a parent at home, engaging with them more meaningfully than at a state toddler farm?