The main theme is likely the struggle against apartheid. In the story, the protagonist probably faces many difficulties and discrimination due to the apartheid system in South Africa. This system segregated people based on race, and the story may show how he overcame those challenges.
Another important theme could be the resilience of the human spirit. Despite living in a very difficult and unjust environment during apartheid, the characters in the short story, especially the main character, show great resilience. They keep on going, keep on fighting for a better life. They don't let the harsh conditions and discrimination break their will to survive and thrive.
One of the main themes could be the power of education. Mark Mathabane might be depicting how education can be a way out of the oppressive situation. The character in 'Kaffir Boy' may use education as a tool to break free from the limitations imposed by the apartheid society. Through learning, he can gain knowledge and skills that give him hope for a better future.