Up to a fifth of child adoptions in Wales break down due to poor and inconsistent services for youngsters and families, claims a report.
The charity Adoption UK said care professionals were not learning from the "unacceptable" level of breakdowns because no overall record was kept.
The charity said families did not always know what help they could have.
The assembly government said it was to consult on measures to "emphasise the importance of permanency" in care.
Adoption UK said its report comes as the number of adoptions in Wales rose from 212 in 2008 to 256 in 2009.
The charity said some local authority services are failing to respond to the emotional and developmental needs of adopted children.
It said there were significant numbers of adoptive families in Wales who are struggling to cope with the demands of "re-parenting a child who has suffered early trauma and loss."
Schools could also be dismissive of the parents' concerns over their child's needs, even though adopted children have a higher than average rate of special education needs, it said.
Wales manager Ann Bell, who is both an adoptee and an adoptive parent, said the number of adoptive family break-ups could be as high as one-in-three but statistics kept by Wales' 22 councils were not collated by the assembly government.
She said: "We feel that the assembly government needs to be pulling that data together and really learning from that data.
"One-in-five is a really unacceptable level of breakdown.
"It is really heart-rending when children have to go back in to the care system when they thought they were going to get a home for life.
"The parents are also really heartbroken when they thought they had a family.
"Adoptive parents do not have enough support to help them through those difficulties."
The charity said fewer than half of adoptive parents know of their entitlement to a statutory assessment, while local authorities have varying levels of expertise in adoption when dealing with traumatised children.
It said it had found that 90% of parents thougth a booklet for school staff outlining the needed of adopted children would have been helpful.
The charity's report makes 12 recommendations including training about children suffering early trauma and neglect for all health and social services professionals.
A Welsh Assembly Government spokesperson said: "We've received a copy of the report and will consider its findings and recommendations.
"We are committed to ensuring the safety and permanence of children who are looked after.
"This autumn, we will consult on a package of measures to strengthen assessment, placement and care planning arrangements for children in care. This will emphasise the importance of permanency.
"Adoption UK is represented on our Adoption and Fostering Advisory Group and we value their contribution to improve permanence for children in Wales."