The correct answer is option 'B', which states that the girls and boys in a town in Madhya Pradesh started going to separate schools from 6th class onwards. Let's understand the reasoning behind this answer.

Background:
In the given scenario, we are told that in a town in Madhya Pradesh, the girls and boys go to separate schools. We need to determine from which class onwards this separation begins.

Reasoning:
To find the correct answer, we need to analyze each option and eliminate the ones that are incorrect.

a) From 5th class onwards:
If the separation started from the 5th class, it would imply that the girls and boys were attending the same school until the 5th class. However, the question clearly states that they go to separate schools. Hence, option 'a' is incorrect.

b) From 6th class onwards:
According to this option, the separation between girls and boys begins from the 6th class. It means that until the 5th class, both girls and boys attend the same school, and from the 6th class onwards, they go to different schools. This aligns with the information provided in the question, making option 'b' the correct answer.

c) From 7th class onwards:
If the separation started from the 7th class, it would mean that both girls and boys attended the same school until the 6th class. However, the question clearly states that they go to separate schools. Therefore, option 'c' is incorrect.

d) From 8th class onwards:
If the separation started from the 8th class, it would imply that both girls and boys attended the same school until the 7th class. However, the question states that they go to separate schools. Hence, option 'd' is incorrect.

Conclusion:
Based on the analysis, we can conclude that the correct answer is option 'b' - the girls and boys in the town go to separate schools from the 6th class onwards.