Extending the school day looks like a win all around. Teachers get more time to prepare for their classes. Students have more time in class for instruction. Parents have more time to get from work to home or school to meet their kids at the end of the day. What's not to like?

But appearances can be deceiving. And that's why communities need to take a clear-headed look at extended school days before jumping on the bandwagon.

Andover has applied for state grants that will fund a study of how an extended school day would work. The town's five elementary schools and one middle school are interested in keeping children in the classroom longer. The $10,000 to $15,000 grants would require administrators to come up with a plan to add 300 hours of instruction to the school year.

That plan would need to be approved by the School Committee and the teachers union before it is implemented. If approved, the town could be eligible for an extra $1,350 in state money per student participating in the longer day.

But what happens when the money runs out? The state has a long track record of encouraging new programs then failing to fund them. Who pays then? Teachers surely are not going to work longer days for free.

Andover's schools have produced outstanding results with the six hours of daily instruction offered right now. Let's think carefully before committing to a much-hyped state initiative that may soon leave taxpayers with an even bigger school bill than they're paying now.