A five year old horse shouldn't have to be ridden with spurs AND a crop already.. something is wrong here.
Just quickly - Spurs aren't a disciplinary tool - I know plenty of 5 year olds who are ridden with spurs for refinement and do great.
Okay. I have sympathy! Latte is also very herd bound. She was 5 when I got her and was still in a paddock with her dam :S.
Horses will always revert to what they learnt first. When Latte gets uppity because the other horses are leaving, I go back to our basic, ridden work at a walk. I ride her in a smal figure eight, small enough that I can get a good bend going. I bend her a bit more than usual, and focus on changing the bend through the middle. If she stops and puts her head up to neigh, the inside rein opens up as astrongly as needed, inside legs goes on, and she needs to get bending around my leg immediatly. The big plus is that this disengages the hindquarters which takes away any ability to rear/buck. I also use my voice - If she scoots her butt under and throws her head up to try and dash toward the others, I will also growl low in my throat while asking her to bend around my leg - The second I get that bend and submission, growling stops, and I just keep her bending forward and continue on our figure eight.
Once I have attention, I move it up to a trot, and I keep it at a trot until she is getting tired. I don't stick to a firgure eight, but I do stick to circles and keeping a bend through her body. I mgiht do two left circles, then one right - make a snowman - Do one big circle then one small. I sometimes halt and back up in the middle of two circles, looking for the bend through the poll and soft back up, then continue on my new circle.