My 4 yr old son started his school(junior kg )this yr .He cant write alphabets.?

Though he can scribble and draw lines he's not able to write curvy letters like B,G etc..His teachers labelled him as the weakest kid in class as all other kids can write very well..They all had done their pre schoolg where they were taught to write .Teachers are complaing every day saying they cant spend time for him..What should i do?How should i make him write ?They are going at a pace of 2 letters A,B(caps and small)and 2 numbers -1 AND 2 per month..