It's an interesting study. The Washington Post reports:
Economist Jennifer Hunt finds that higher levels of immigration actually increased high-school graduation rates among native-born children, particularly among black students. Examining Census data from 1940 to 2010, Hunt explained her research in a new paper for the National Bureau of Economic Research:
An increase of one percentage point in the share of immigrants in the population aged 11-64 increases the probability that natives aged 11-17 eventually complete 12 years of schooling by 0.3 percentage points, and increases the probability for native-born blacks by 0.4 percentage points
The main reason the increase, she says, is that native-born children have a larger incentive to complete school in order to avoid competing with less-educated immigrants for low-skill jobs.
Anti-immigrant groups like to try and divide the left and center-left by arguing that immigrants hurt the poor by competing for their jobs. But perhaps some competition is beneficial if it is causing people to improve their educational credentials and, consequently, their earning power.