My three youngsters seemed to turn into monsters after visiting with their grandpa and grandma. The kids' manners deteriorated and they whined about family chores and routines. It was a day or two before they shaped up and behaved normally. "Who needs grandparents?" I sometimes wondered.

Now that I'm the grandfather of eight grandkids, my perspective has changed. I agree with family psychologist and author John Rosemond who said, "Grandparents should be gentle teachers of the way life was and the way it always should be."

But it doesn't work that way if the parents' development is affected by unclear boundaries between parents and grandparents. An angry mother wrote the following note to Cathleen Brown, a San Jose Mercury News columnist: "My parents live an hour's drive away and visit us and our two sons frequently. The problem is my mother takes it upon herself to discipline kids as if she were the parent even when I'm in the same room. No matter what the boys do, she seems to find something to correct . . . I feel she overlooks the fact that I am their mother and is indirectly criticizing me. Am I wrong to feel upset?"

Instead of a gently teaching her grandchildren, she overstepped her bounds by disciplining her grandsons and criticizing her daughter. Because she misunderstood the role of grandparents, her grandchildren missed their most valuable resource.

Here are some ways to assure that you become a gentle teacher of your grandchildren.

Pay attention to family rules and discipline
A good discipline pact allows grandparents to handle minor discipline problems while the parents take care of any serious breach of rules. Otherwise a grandparent's attempt to smooth things over may end up undermining family discipline.

Update your parenting skills
To avoid clashes over discipline ask your grandchild's parents to explain how they correct unacceptable behavior. Practical questions like, What should I do if my two-year-old granddaughter pitches a tantrum in the supermarket? Does ignoring the tantrum work better than a swat on the behind?

Review specifics
Ask for a review of family rules governing television-viewing, use of the family PC, completing homework and inviting friends over. As an unsuspecting grandparent you may believe your grandchild is in her room with a classmate researching a homework assignment on the Web. Instead, she is watching forbidden TV or exploring banned Internet sites.

Talk about problems
When the grandparents of my children visited, the eating habits of my daughter often dominated the table talk. She was a picky-eater. And it didn't matter whether her tummy was full or she simply wasn't hungry, grandma would comment on her untouched food.

Once, after failing to coax her to eat, her grandmother picked up my daughter's fork, stabbed a veggie and began to feed her. Of course she delighted in the attention, while I squirmed in my chair and did a slow burn. I wanted to scream, "Don't, she's 10 years old!" But I couldn't say a word without causing a major scene.

Looking back, a picky-eater's policy for our family would have helped. With a policy in place, we could have discussed our daughter's eating likes and dislikes, and my digestion would have improved.

Emphasize your values
As grandparents you have a set of values to transmit to your grandchildren. Ones that worked for you, like respect, honesty and responsibility. "Grandparents who keep a spiritual perspective as a vital part of their lives open a window for their grandchildren that allows them to catch a glimpse of all that life was meant to be," say Stephen and Janet Bly, authors of How to Be a Good Grandparent. (Moody Press, 1990).

The influence of a grandpa or grandma who cuddles his grandchild in his lap and shares a favorite story can’t be measured. But the powerful effect of grandparents on the lives of their grandchildren is clear. To gently teach your grandchild about the way life should be is to give him or her an unforgettable glimpse of life. And that’s the reward. You can touch the lives of your grandchildren.