Wares was arrested under a UK extradition warrant in October last year before being released on bail. A hearing is scheduled to take place on 16 April.
His accusers include BBC presenter Nicky Campbell, who was not abused by Wares but has said he witnessed the sexual abuse of a pupil by the teacher.
South Africa’s national prosecuting authority said the additional charges included 60 counts of sexual assault, four of rape and 25 of assault.
Wares denies the charges and has fought against the extradition.
Laura Connor of Thompsons Solicitors, which represents many of Wares’ former pupils in Scotland, said there were likely to be some mixed emotions at the verdict.
“It is quite a monumental point in proceedings where we now have Iain Wares as a convicted sex offender,” she said.
“I believe this may be the first of many convictions, provided that further proceedings are progressed with the necessary urgency.
“It is now essential that all relevant authorities work together to ensure that this convicted child sex offender is extradited to Scotland in April, so that he can face justice for the extensive offences he committed here.”