Laura Byrne is a journalist and not a scientist so she doesn't know a control group from a hole in the wall. Kids without preschool in the national study she quotes had good home care and all the study shows is that good home care is on par with preschool. The study is not concerned with poor children who have no such good home care.

The Perry historical study is very well done and IIRC has been validated by another similar experiment and statistical studies of these kids. Any historical study is very difficult to do because the study still be valid 20 or 30 years into the future. The results of the study are statistically significant for the sample size. IOW the results that are significant cannot happen by chance but only by the change in experimental condition of the test group.

The Stanford study IIRC is concerned with academic oriented preschool programs like prekindergarten which have good results in the short term but cause long term problems. No needy kids here.