What does he mean by "I can't keep it straight."?

Rebecca

To "keep it straight" means to avoid confusing or mixing something up. The speaker means that there are so many classes that the "little ladies" (his daughters) have to go to, that he can't keep track of them/can't avoid getting them all mixed up. Ex: How many brothers and sisters do you even have?! There are so many I can't keep them straight. Ex: There were so many names to memorize that I had a hard time keeping things straight.