Well socialized puppy showing aggression

I'm after some advice about my 6 month old puppy showing aggression towards other dogs and people when we are out for our walks. Her fur stands up on the back of her neck and she starts barking and lunging at anybody and animals she sees, even when they are only in the distance.

She is a well socialized dog. Went to puppy class and she current goes to doggie daycare two days a week (spends all day with 20-40 dogs of all ages and sizes)and she has been having play dates once a week with puppies of the same age as her since she was very young.
She gets along fine with all these dogs, staff at daycare and the dogs owners and any visitors we have over to our place. We have a pet cat and two rabbits which she also gets along well with.

She does not act like this at home, she is the most cuddly, loving affectionate dog, the aggression is only once we have left our place.

I do find that if she is given the chance to come into contact with a dog she has been barking at and gets a chance to sniff them she relaxes but most dog owners don't want her near them or their dog when she acts like this.

Could it just be excitement? Or fear? She often also tucks her tail between her legs and shakes when barking etc

Her lead manners is not 100% but we have been working on it. She still needs to learn to walk beside me and sometimes pulls on the lead but she is improving. I live near a river and try to walk her along the river to try and avoid coming into contact with other dogs and people.

I don't know what to do. Telling her off doesn't work, it just gets her going more, I have just been turning around and walking in the other direction but she will still bark and try to get to them.
A friend suggested using a shock bark collar when out walking but I'm not to sure about this. What are your thoughts?

I would like to stop this before she gets too big!

Any advice would be much appreciated.

Thank you heaps

Firstly, don't worry too much. This is very common and there are things you can do to help.

I personally think it's a combination of excitement and lack of confidence. What she needs to learn is that she can deal with meeting other dogs quietly. It's not the easiest lesson in the world and might take some time but with a consistent approach from you it is possible. The hardest thing, as you've possibly already discovered, is other dog owners!

The first thing is to teach Sadie 'this way!, which means 'hey, come to me for a treat/play', whichever she finds the greatest draw. It's different from recall, all you want her to do here is follow you as you either back up or turn around and run off a few paces. All you do is call 'this way!' like it's a huge game, back up 4 or 5 paces and reward/play in a really happy way when she comes. You become a really fun place where she gets something good.

Get this solid at home, in the garden, on a quiet walk away from others, anywhere where she can concentrate on you. Do it from time to time randomly so that Sadie learns to do it anywhere. Start when there are no distractions, then build up gradually to more testing situations. If any any point she finds a distraction a bit too much and she doesn't come, resist the urge to use the lead if you can and up your call. Stick the treat/toy under her nose maybe. Then learn that that level of distraction is still too much for her and don't ask it of her just yet. Go back to something easier.

It's not only the level of distraction, it's also how close it is that matters. Another dog isn't a problem in the next town but is when it's 5 metres away. Finding the distance that she starts to feel she needs to react is important. That might be a way away at the moment.

When you are out and about, when you see another dog, before she's got a chance to even think about it, call her to you. When you have her with you, you can close the gap, keeping an eye on her body language. At the first sign that she's anything other than fully relaxed, call 'this way' and bring her to you again. This is more of a mental than a physical thing, you want her mind with you, not focussed on the other dog.

What you should find is that she relaxes and that the distance between you and other dogs before she starts to tense decreases as she learns how to act. Remember to praise and reward when she looks at other dogs in a quiet way.

Don't tell her off or punish her for over reacting. And never, ever use a shock bark collar. One of the best ways to make a dog worried by other dogs is to introduce something real for them to worry about.

It's a relief to know it's common. We will give this a go.
Thank you so much!