The west end site of Laurel Park will become a coeducational primary. All secondary pupils will go to the southside Hutchesons' campus, which will retain its primary.
A joint statement by the chairs of the boards of governors said that the merger rmoves "uncertainty and guarantees a stable, long-term education for all Laurel Park pupils".
There are only 107 pupils in the Laurel Park primary. The governors believe that is insufficient to provide senior school subject classes beyond 2002. Therefore they "had to take rapid, determined action".
But Robert Kerr, of the parents' action committee, said there would be a vigorous campaign of opposition.