This is a volunteer run organization based in the United States that may be good to contact about partnering with your NGO to help the school. It looks like they provide support with fundraising and also volunteers on the ground.

http://www.cameroonsupportorganization.org/school_new.html

I think it would be good to contact them and provide an introduction to Goodness and Mercy Missions to see if they might be able to partner with you.

Regards-

Jennifer