We have a cockapoo male who's now about 9 months old. We had exact same experience as you. In a daycare setting, or any setting where he got over excited or overstimulated, he would mount constantly. Daycare tried to accommodate it but in the end were saying it wasn't fair on the other dogs having him there. 2 things worked for us.

First was having him around dogs in a less full on environment. We signed him up for group dog walking with a local company. He still mounted, but it was a smaller more controlled group and he was a bit better as a result. He improved a lot but when he went back to daycare would still mount.

Then on the advice of our vet we neutered at 6 months. That made a huge, huge difference. From about a fortnight afterwards the mounting behaviour began to slow, then after about a month it went entirely. He now needs to be seriously, seriously over excited to mount. At daycare etc they've said he's a completely different dog.

Tbh a lot of people on here repeatedly told me I wasnt training him enough, or suggested it was my fault somehow. I was also repeatedly told it was dangerous to neuter at 6 months too. But neutering has helped immensely so I suggest asking your vet what they think.