The Communities Empowerment Network, which advises people who believe they have been mistreated in education, is angered by plans to change the composition of panels which review exclusion decisions to include present or former teachers.
The lottery-funded group says staff will be less sympathetic to black pupils than others in the community because they are more likely to be white and take the school's side.
Director Gerry German expects the network's exclusion caseload to surge to more than 100 a month because of the change. He predicted new members would be retired white staff "with a greater willingness to rubber-stamp headteachers' decisions".
Although exclusions of black pupils are falling, they remain three times more likely to be excluded than their white peers.
A Department for Education and Skills spokeswoman said there was no reason to suspect more black children would be excluded after the changes.
Eamonn O'Kane, general secretary of the National Association of Schoolmasters Union of Women Teachers, also dismissed the network's fears. "If more teachers are on the panels it will be a benefit to all pupils, irrespective of their colour. We are very concerned about acting in a non-discriminatory manner."