Step 1: Understand the question.
We must find the likely outcome when a teacher holds prejudice toward children.
Step 2: Recall the effect of prejudice.
Prejudice brings bias, discrimination, and negative expectations into the classroom.
Step 3: Test option A.
Confidence would not increase; biased treatment makes children feel undervalued, so it is wrong.
Step 4: Test option B.
Learning speed would not rise; stress from bias slows performance, so it is wrong.
Step 5: Test option D.
Discipline does not improve through prejudice; it breeds resentment, so it is wrong.
Step 6: Confirm option C.
Children's emotional, social, and academic development is harmed, so development is negatively affected.
Step 7: Conclude.
Hence the realistic outcome is option C.
\[ \boxed{\text{C. Children's development will be negatively affected.}} \]