Capital appreciation bonds have become increasingly popular across the state, since they allow school districts to borrow money now without raising taxes on current residents. Instead, the burden for paying for the bonds is pushed to future generations, who are left on the hook for loans that are wildly more expensive than conventional bonds.

San Diego Unified — Borrowed: $164 Million. On the Hook For: $1.25 Billion

In 2010, the county's largest school district borrowed almost $164 million from investors using capital appreciation bonds.

The loan was part of 2008's Proposition S, in which voters approved the district to borrow more than $2 billion to complete district-wide renovations and modernization.

Just like Poway, San Diego unified won't start paying back those bonds for 20 years. The first payment is due in 2030. By the time the loan is fully paid back, in 2050, San Diego taxpayers will have paid back $1.25 billion, or about 7.6 times what the district borrowed in the first place.

That's much more expensive than a typical school bond which, like a home mortgage, is paid back every year of the loan. In a more typical bond, a district would pay back two or maybe three times the total amount of the initial loan....