Paul Greig, 51, is alleged to have attacked the youngsters when he was aged just 14.
The alleged victims are said the have been aged between 6 and 7 and 8 and 9 at the time.
Giving evidence one of the alleged victims, now aged 43, said she was "terrified" of Greig.
Lothian and Borders Police employee Greig is alleged to have carried out the abuse between February 1974 and February 1975 at an address in West Lothian. He denies the allegations.