I would certainly consider it inappropriate to say those words in the way you relayed them to us. Teachers generally should not give unsolicited advice to parents about how to raise their children; rather, they should give feedback to the parents as to how the child is doing in school. This can convey much the same information, but in a more respectful manner:
Please teach Johnny better table manners!
At lunchtime, Johnny is often seen to be eating with his hands and making quite a mess of the table.
The latter is appropriate; the former is not, as it implies you don't teach him manners to your satisfaction.
In the case above, the teacher should have described the behaviors, and then asked (politely) for your help in managing them.
Schools might sometimes give general advice to the population of parents, however; i.e., sending home fliers about how to talk to your child about X topic, or similar. That's much more appropriate, as it doesn't single you out and is instead simply providing reference material to those who want it.