I live in a pretty big house in the countryside with a couple acres of land. Sounds like dog heaven, right? Maybe not. I'm still at school so I live with my parents and we have two dogs. One dog is a 5 and a half year old border collie who I got as a present for getting through some pretty tough stuff at school one year. She came from a working dog family. Our other dog is a cocker spaniel who just turned one. My mum hates (and always has) the collie but adores the spaniel and lets him get away with everything (by that I mean chewing, jumping up, getting on sofas, getting mud everywhere, the lot). He is always allowed out of the kitchen (which is where they sleep) but the collie isnt because she doesn't sit still much and she gets fur everywhere. As school has piled on the work recently, I haven't had much of a chance to walk her but she generally gets nice long walks around three times a week and we take in into the garden to play fetch (admittedly not very well as she doesn't like to drop the ball) until she's knackered every day. But here's the thing. The collie was raised around kids as my oldest siblings have children she's always known (they were about 3 when we got her) and she's always been generally pretty good with the exceptions of a few occasions where she's tried to play and someone got a little bruised up. We generally just accepted this because she never acted aggressively or meant any harm, the kids just didn't know any better and she doesn't know how big or strong she is. However recently she has started growling at people in an aggressive manner, especially children. Although she's never done anything to worry anyone who lives in the house, she's started growling at kids even the ones she knows. She only growls at some strangers that are adults. There was a pretty weird incident where my sister invited some of her friends round for drinks and the collie was fine, but not two weeks later when I invited my friends round, she growled at some of them. She would go up and ask for a fuss and then growl when they stopped. The weird thing was it was only three of them she would do this with and she had met one of the three before. As this behaviour is increasing in frequency, my mum said that she is going to get rid of the dog if nothing changes. I told her that before doing that, we should at least ask a vet or trainer for help. My mum said that she doesn't see the point in a trainer but is willing to ask the vet and some friends who have had aggressive dogs before. I love my dog a lot but we've tried so many things. When there is someone in the house or she hears something that she thinks could be an intruder (ie. door knocking, someone pulling up on the drive) she barks constantly and there is no stopping her unless there is someone there with her. With the new aggressive habits I really worry that this is it as we have a lot of people round often so an aggressive dog simply won't work for us. Any advice or tips would be so appreciated.