Introduction:
The line "A child cannot forget his youthful spring" is from the poem "The School Boy" by William Blake. This line encapsulates the theme of the poem, which explores the loss of innocence and the longing for freedom experienced by a young child in a restrictive educational system.

Main Body:

1. The significance of youthful spring:
- The phrase "youthful spring" refers to the carefree and joyful period of childhood, symbolizing the child's innocence, curiosity, and natural inclination to explore and learn.
- During this phase, children are full of energy and enthusiasm, eager to experience the world around them.

2. Loss of innocence:
- The poem reflects on the transition from the freedom of childhood to the restrictive environment of formal education.
- The child is depicted as being confined in a classroom, feeling trapped and longing for the freedom he once had.
- The loss of innocence is portrayed through the imagery of the "caged bird" and the "sighing and dismay" of the child.

3. Nostalgia for the past:
- The line "A child cannot forget his youthful spring" suggests that even as the child grows older, he cannot completely forget the carefree days of his childhood.
- The memories of the joyful experiences and the sense of freedom remain deeply ingrained in his mind.
- This nostalgia for the past highlights the longing for the innocence and simplicity of childhood.

4. Critique of the education system:
- The poem is a critique of the formal education system that suppresses the natural instincts and creativity of children.
- It portrays the classroom as a confining space that stifles the child's spirit and prevents him from fully enjoying his youth.
- The contrast between the "leaping gladness" of the child's heart and the "sighing and dismay" in the classroom highlights the oppressive nature of the education system.

Conclusion:
In conclusion, the line "A child cannot forget his youthful spring" emphasizes the profound impact of childhood experiences on an individual's memory and psyche. The poem "The School Boy" explores the loss of innocence and the longing for freedom experienced by a child in a restrictive educational environment. It serves as a critique of the education system and reminds us of the importance of nurturing a child's natural curiosity and joy in learning.