A cataloguing dilemma

Many books at our library have been incorrectly classified and I have spent a lot of time reclassifying them.  This is for the benefit of students, for example if books on special education are scattered around the library and not generally in one section, it makes it harder for them to browse and find what they want.  Here are some examples:

• Books in the 700's - Arts, that should be in the teaching section, the 372's because they are about teaching art to children. 
• Books on caring for young children in the 649's - Parenting, that should also be in the 372's because they are written for teachers, not parents.  
• Books on children with learning disabilities in the 618's - Health, which should be in the 371's, the section on special education.
• Books in the 153's - Psychology, which are about psychologists like Vygotsky and how their work relates to teaching so they should be in the 370's.

Recently I came across a book called Research Methods in Early Childhood.  This was classified as 370.7 and I thought I would change it to 370.72 like most of the other books on doing research in education.  Then I checked the online classifying tool Classify and it said most libraries classified it as 372.21072.  I didn't want to put it there, I wanted to put it with most of the other research books in 370.71 or 370.72.  Then I checked what AUT Library classified it as and I was surprised to see it was 305.23 - Young Children.  The books in the this section are mostly on child development - it would look out of place there.  In the end I went with 372.21072, though why it should have that particular classification I'm not sure.  I guess it goes to show there is not always a right or wrong when it comes to cataloguing.