A dramatic increase in 1993 in how much parents are permitted to borrow from the federal government for their children’s college is coming home to roost. Since then, average debt through the parent PLUS loans has more than tripled, adjusted for inflation, according to a Brookings Institution report. About one in 10 parents owe more than $100,000. And as loan balances have ballooned, the rate of repayment has slowed. Now that the college applications have been submitted, Allan Katz, a financial adviser in Staten Island, New York, has this advice for parents contemplating their next move: PLUS loans should be avoided “at all cost,” he said. “A big part of my practice is avoiding PLUS loans.” His dire warning stems…