"Taking your school away (after) having been through 10,000 quakes is one of the most abusive things you can do to a child."
Coleman said the decision was made without any consultation.
He also said the Government would target small schools throughout the country after dealing with Christchurch.
"We're asking the Government to come down and listen to the affected communities and affected schools."
Another rally organiser, Wayne Hawker, said he was delighted with the turnout. He said more protests were planned, including a "major street march".
Hawker said concerned parents, principals and students joined politicians at the rally. "This is about our kids."
He said so many people drove in to join the rally, a traffic backlog caused a 15-minute delay to the protest start.
Kendal School was one of 13 set to shut because of the overhaul. "Our neighbourhood schools are too valuable to lose," Kendal School supporter Mary Tingey wrote online. "Children need small, friendly places in which to grow and learn. They are the focus of our communities."
Avonside Girls' and Christchurch Girls' were targeted for a proposed merger, as were Shirley Boys' and Christchurch Boys'.
Yaldhurst, Richmond and Greenpark schools were also in the firing line, to the dismay of protesters, including tearful schoolchildren.
