**Core Concept**
Schizophrenia is a complex and multifactorial psychiatric disorder that has been linked to various socio-economic, genetic, and environmental factors. The disorder's etiology is not fully understood, but research suggests that individuals from lower socio-economic backgrounds may be more vulnerable to developing schizophrenia due to stress, poor access to healthcare, and other environmental factors.

**Why the Correct Answer is Right**
Studies have consistently shown that individuals from lower socio-economic strata are at a higher risk of developing schizophrenia. This may be due to increased exposure to stress, poor nutritional status, and limited access to healthcare services, which can exacerbate the onset and progression of the disorder. Additionally, individuals from lower socio-economic backgrounds may experience social isolation, which can further contribute to the development of schizophrenia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as there is no evidence to suggest that schizophrenia is more common in higher socio-economic strata. In fact, many studies have found the opposite to be true.

**Option B:** This option is incorrect as schizophrenia is not more common in the middle class. While individuals from the middle class may experience stress and other environmental factors that contribute to the development of schizophrenia, they are not at a higher risk compared to individuals from lower socio-economic strata.

**Option C:** This option is incorrect as schizophrenia is not more common in individuals with a high level of education. While education may provide individuals with better coping mechanisms and access to healthcare services, it does not protect against the development of schizophrenia.

**Option D:** This option is incorrect as schizophrenia is not more common in individuals from a high socio-economic background. In fact, many studies have found that individuals from lower socio-economic backgrounds are at a higher risk of developing schizophrenia.

**Clinical Pearl / High-Yield Fact**
It is essential for clinicians to be aware of the socio-economic factors that contribute to the development of schizophrenia, as this can inform treatment and management strategies. Providing individuals from lower socio-economic backgrounds with access to adequate healthcare services, nutritional support, and social support can help mitigate the risk of developing schizophrenia.

**Correct Answer:** C. Lower socio-economic strata