when i took lee to nusery school hed cry and cry to the point i used to ring after 10 mins of me being gone , so what they did was had him for so long a day it started at 30 mins then when to 60 then 90 and so on so he knew id be deffo comming back we did this for a week then till he was being left for 2half hours , that worked with lee,
good luck debxx