As mentioned in the comments the "seven dollar" claim is supported by one study. According to this factsheet, there are at least individual studies that support some of the other claims as well.
- Graduation: "Chicago children who attended an early childhood education program were 29% more likely to graduate from high school than their peers who did not attend."
- Crime: "Chicago children who did not attend early childhood education programs were 70% more likely to be arrested for violent crime by age 18 than their peers who had attended.
- Pregnancy: "North Carolina children who attended early childhood programs were less likely to become teen parents than their peers who did not attend (26% vs. 45%)."
I haven't hunted for the references to verify these statements, but the first two may refer to the same Chicago study that the seven dollar figure comes from.
There have been several comprehensive meta-studies of the general issue. Here is one published in 2010 that states:
Consistent with the accrued research base on the effects of
preschool education, significant effects were found in this study for
children who attend a preschool program prior to entering kindergarten.
Although the largest effect sizes were observed for cognitive
outcomes, a preschool education was also found to impact children’s
social skills and school progress. [emphasis added]
Here is another good source from 2013, which draws similar conclusions:
Most evaluations of early education programs show that such programs improve children’s school readiness, specifically their pre-academic skills, although the distribution of impact estimates is extremely wide, and gains on achievement tests typically fade over time. Some studies of children who attended preschool 20 or more years ago
find that early childhood education programs also have lasting effects
on children’s later life chances, improving educational attainment and
earnings and, in some cases, reducing criminal activity. High-quality
early childhood education programs thus have the potential to generate
benefits well in excess of costs. [emphasis added]