Introduction:
In the novel "Across Five Aprils" by Irene Hunt, Mr. Lamb is a schoolteacher who is known for his kind and understanding nature. When he refers to Derry as "blessed," he is highlighting a specific aspect of Derry's life that sets him apart from others.

Explanation:
Mr. Lamb calls Derry blessed because, despite having a burnt face, he possesses a perfectly healthy body. This statement implies that Derry's physical appearance may not be ideal, but his overall health is intact. Let's delve into the reasons behind Mr. Lamb's perspective:

1. Derry's Burnt Face:
- Derry's burnt face is a visible and significant physical feature that sets him apart from others.
- The burn may have resulted from an accident or some unfortunate incident in Derry's life.
- This physical disfigurement could potentially lead to social isolation or discrimination.

2. The Significance of Good Health:
- Mr. Lamb recognizes that good health is a blessing in itself.
- Derry's perfectly healthy body suggests that he does not suffer from any debilitating physical conditions or illnesses.
- This contrasts with the many individuals who may face health challenges or disabilities.

3. Appreciating the Positive Aspects:
- Mr. Lamb's perspective reflects his ability to see beyond physical appearances and focus on the positive aspects of Derry's life.
- By calling Derry "blessed," he highlights the importance of appreciating what one has rather than dwelling on what one lacks.
- This perspective encourages empathy, compassion, and a deeper understanding of one another.

Conclusion:
In summary, Mr. Lamb calls Derry blessed because, despite his burnt face, he possesses a perfectly healthy body. This statement emphasizes the significance of good health and encourages readers to appreciate the positive aspects of life, regardless of physical appearances. It also showcases Mr. Lamb's compassionate nature and his ability to see beyond superficial differences.