Alaska has had to deal with an extreme version of this issue for a long time. One mitigation that the state has come up with is to offer competitively priced student loans to Alaska residents who are bound for colleges across the US. The interest rate on the loans is further lowered if you live in Alaska after graduation, incentivizing educated Alaskans to come back. Those students are also likely to have maintained their Alaska residency to qualify for the Permanent Fund Dividend (an annual payment that comes from rolling returns on the state’s sovereign wealth fund).