Hello!

I am running a Difference in Difference (DD) regression to see whether the introduction of a policy affected school enrolment for a particular social group (S1) as compared to three other social groups (S2, S3, S4) and I have data from before and after the policy was implemented.

The command for the regression is:
reg school hh_S2 hh_S3 hh_S4 post post_X_S2 post_X_S3 post_X_S4

where hh_S2 = 1 if the household belongs to the social group S2 and 0 otherwise and so on for S3, S4, S5
and post = 1 for years after the policy and 0 for before the policy

I am more interested in seeing the effect of the policy on S1 school enrolment because that is my treatment group. My question here is that since I have multiple control groups rather than one treatment and one control group, what would be the interpretation of the coefficient for the constant term as well as the post coefficient. Is the coefficient for 'post' the effect of the policy on school enrolment for social group S1 after the policy and coefficient of constant the expected school enrolment for social group S1 before the policy?

Thank you