When Kaci Taylor Avant got caught cheating on a test a few months back, the teacher called her mother, who was nothing less than stunned. After all, Kaci always does her homework and gets mostly As in school. Mother and daughter had already had 'the talk' about how cheating was wrong. And then there's Kaci's age.

'I had to ask myself, 'Wow, really? She is only 8!' ' says her mother Laina Avant, a Paterson, N.J., network engineer.

As school-testing season heats up this spring, many elementary-school parents are getting similar calls.

The line between right and wrong in the classroom is often hazy for young children, and shaping the moral compass of children whose brains are still developing can be one of the trickiest jobs a parent faces. Many parents overreact or misread the motivations of small children, say researchers and educators, when it is actually more important to explore the underlying cause.

A growing body of research suggests responses for parents, adjusting strategies in subtle ways by each age.

The challenge with 5- and 6-year-olds is helping these little black-and-white thinkers liken cheating with other actions they already know are bad. Most children understand as early as ages 2 1/2 to 4 that it is wrong to hit, shove or tease another child, says a 2012 study in the journal Child Development. And preschoolers typically know it is wrong to cheat at games. 'But translating that understanding from a game situation to an academic situation is a huge leap,' says Eric Anderman, a professor of educationalpsychology at Ohio State University in Columbus, Ohio.

First- and second-graders are often taught to work together and share ideas in small classroom groups. When told they must start working independently, 'it's naturally confusing to a 7-year-old,' Dr. Anderman says. By third grade, 'the high pressure starts' as more students begin taking state standardized tests, says Mark Terry, president of the National Association of Elementary School Principals. Most schools also begin giving grades, and children may cheat to keep up or to please parents or teachers. Children with poor study skills or learning disabilities are especially vulnerable; poor impulse control is linked with a higher readiness to cheat, says 2010 study of 189 children in the Journal of Clinical Child & Adolescent Psychology.

Other children start feeling pressured at this stage by busy sports and activity schedules that don't allow time to study, says Kenneth Shore, an East Windsor, N.J., author and psychologist. 'Parents can get a little panicky' and compound the problem by orchestrating kids' science projects, dictating sentences or typing their kids' essays, he says. Not only does this send the message that presenting someone else's work as your own is OK, but it suggests that grades are more important than learning -- an attitude linked in research to higher rates of cheating. By fifth grade, 'peer pressure to cheat is huge. If somebody asks you for answers and you don't share them, it can be a major offense among the kids,' Mr. Terry says. Parents can help by giving a child an out: 'Well, you know I'd share it with you, but my dad would kill me if I did.'

More schools are allowing cellphones in classrooms, expanding opportunities to cheat via text message, photos or stored notes. And research shows that while most fifth-graders know that copying words off the Internet is cheating, many don't understand 'exactly how much is too much to pull from a source, and how to paraphrase information,' says Kimberly Gilbert, an associate professor of psychology at Hofstra University in Hempstead, N.Y.

About 30% of elementary students report cheating when asked on anonymous surveys, according to a seminal 1999 researchreview that is still cited by researchers and administrators. Some researchers believe the incidence is rising. 'We hear about cheating happening more and more, at younger ages,' especially as younger children bring more mobile devices to school, says Dr. Anderman, who is co-editor of a reference book on academic cheating. Mr. Terry estimates about 1 in 3 students cheat at some point during elementary school.

Cheating rates rise through middle school and by high school, 51% of students admit to cheating on a test in the past year, and 74% say they have copied another student's homework, according to a 2012 survey of 23,000 high-school students by the Josephson Institute of Ethics, in Los Angeles, a nonprofit character-education organization. Founder Michael Josephson says the findings reflect 'a pervasive cheating culture.'

All of which heightens the need for parents to teach and model strong decision-making behavior to their younger children, who are becoming vulnerable to such pressures at ever-earlier ages. Dr. Shore advises parents to 'take a breather' to calm down if they receive a call about their child cheating. Then, he advises telling the child you're disappointed, cheating is unacceptable and it mustn't happen again. Beyond that, says Dr. Shore, it is important to meet with the teacher or principal and help the child figure out what kind of pressures or stresses led him to cheat.

Ms. Avant got the call about Kaci's cheating while commuting home on the bus from her job at a New York City law firm. Horrified and embarrassed, she had time to calm herself before picking Kaci up after school.

When Ms. Avant asked her daughter that evening why she cheated, Kaci said she was afraid her mom would be angry over a bad grade. 'When she said that, I thought, 'Wow, maybe I need to check myself,'' Ms. Avant says.

A former college athlete, and founder of a girls' T-shirt company, Ms. Avant says she has always spoken loudly to assert herself. But she realized that using that tone of voice with Kaci, and demanding that she study and put forth her best effort at school, made her daughter afraid to admit she sometimes didn't understand her homework, Ms. Avant says.

Ms. Avant explained to Kaci that cheating was wrong, said she was disappointed in her and met with her teacher and principal. She says she also spends more time now going over homework, lowering her voice and encouraging Kaci to 'be more up front' when she doesn't understand something. Kaci has since been showing her mother all her papers, including answers she got wrong. The third-grader still gets mostly As, and she has learned that 'cheating is bad,' Kaci says in a phone interview. If she doesn't know a test answer, 'I just do the best I can,' she says.

For parents, stressing intrinsic goals, such as mastery, learning and doing one's best, can be tough. But research shows it is one of the best ways to prevent cheating.

Lisa Endlich Heffernan, mother of three sons who are now 17, 20 and 21, says she tried to instill a sense of right and wrong by teaching them starting in elementary school that cheating was like lying. If facing a choice between cheating or getting a low grade, she told them to 'take the D,' says the Bedford Hills, N.Y., author and parenting blogger at GrownandFlown.com.