The Senate yesterday unanimously approved and sent to President Clinton legislation aimed at making college more affordable by increasing grants and lowering interest rates on student loans.

The five-year reauthorization of the Higher Education Act emerged from a conference committee as a compromise that incorporates both Democratic and Republican priorities, and that extends special incentives to students who want to become teachers. More than half of college students take advantage of the loans and grants authorized by the federal government.

This provision could save students $700 on an average debt of $13,000, said Senator Edward M. Kennedy, one of the conferees. The provision would cover new loans, but would give students with existing loans four months to consolidate their debts to take advantage of the lower rates and effectively refinance. At today's market prices, the interest rate would drop to 7.46 percent from 8.25 percent.