Complaints fell to 52 in the 2007-8 academic year, compared with 99 the previous year.
Teachers' unions this week welcomed the reduction, saying it showed that schools were handling complaints better and were less likely to be "overcautious" by recommending that cases be taken out of their hands.
Gareth Jones, Welsh secretary of the Association of School and College Leaders, said it would end unnecessary stress for those teachers falsely accused by pupils.
"We had a lot of concerns about this procedure, certainly during its first year of operation," he said. "There seemed to be a culture of investigating just about everything."
The Assembly government appointed ServocaDream, formally trading as the Dream Group Ltd, to handle cases two years ago, in response to recommendations contained in the landmark Clywch report, launched in 2004.
In the report, Peter Clarke, Wales's late children's commissioner, made 16 recommendations to tighten up child protection in schools. One was that abuse claims against teachers should be handled independently of schools and local authorities.
The recommendations followed his inquiry into the "cover up" of child abuse allegations made against John Owen, a drama teacher at Ysgol Gyfun Rhydfelen, a secondary, in Pontypridd. He committed suicide in 2001, before appearing in court charged with a string of sex offences against former pupils in the 1980s and 90s.
Last week, eight of Mr Owen's alleged victims won compensation for negligence from Mid Glamorgan Education authority - now Rhondda Cynon Taf council - in out-of-court settlements.
Servoca employs retired police officers and detectives to investigate cases, but there has been criticism of the methods deployed by case workers, including the formality of interviews.
David Evans, secretary of the National Union of Teachers Cymru, believes schools are being better advised on which allegations need further investigation.
"Many of the cases that were referred originally were matters that should and could have been dealt with at school level," he said. "Perhaps schools were being over-cautious."
It was originally estimated that about 20 cases a year would be referred to the independent body.
Bob Sherwood, of Servoca, said inquiries were being dealt with appropriately and meetings with teachers were not conducted as formal interviews.