Not ready to go to school or anywhere.

My child is 3 yrs old. Since birth we found out that she is scared of darkness. Now when she started going to school she is not ready to be left there simply without mummy. We changed school, thinking she might be facing adjustment problem.other school she adjusted in A weeks time, it's been almost a year now but on and off she faces same problem. Not ready to go to school. Cries a lot and vomits and if her mummy stays back she enjoys. Tried explaning a lot of time taking names of classmates, friends teachers and whatever possible. She screams even if someone else touches her at school, clutches like a monkey to her mom. We even tried enrolling her for dance classes which she likes a lot (thought of giving her exposure, new area) there also initially she enjoyed, almost like 3 months now but here again same thing has started creaping in, mummy has to be there. She might stay back but won't dance will take a chair and sit for the whole class at the back @ school doesn't even open tiffi