What was the name of that manga where the little girl with long pigtails was in love with her teacher?

Okay, there's a manga about 3 little girls, 1 who was verbally abused by a previous teacher, another with long red pigtails who is in love with her teacher and a third little girl with black hair who is in love with the girl with pig-tails. The pig-tailed girl's name began with an R or something (it might have been Rin -- let's say Rin) and she was the ring leader of the trio. Does anyone know the name of this manga?