There aren't many things teachers dread (especially new teachers) more than the parent phone call home.
On the contrary, I've found that about 90% of the time I call home, parents are fully supportive. Here's what has worked for me:
"Hi ____ , I'm ______ teacher and I wanted to reach out to see what recommendations you have in working with him/her."
Of course, this is a very different approach than, "Hi _____ , I'm ______ teacher and ______ is a major disruption in this class. He/she is going to get a detention and if he/she continues the acting that way, _____ will face more serious punishments (of course we don't actually speak this way).
See the difference? It's extremely effective.
Also, when's the best time to reach out to parents? Immediately! If it's the first day of school, then that is when the phone call needs to happen. Remember, no one student should be allowed to prevent other students from learning.
Try it! I guarantee you'll see a major difference in many of your kids' behaviors!