From my experience, training would be apart of your daycare experience. You can pay for additional training to help, but whomever is supervising the group should be correcting those behaviors immediately. Daycare shouldn’t just be a free for all, and it is beneficial to the person managing the group to manage those behaviors anyway.
It sounds like your dog is most likely learning those behaviors from another dog that goes there, or at least being put in situations where he needs to be snappy. At 3 months old he is learning how to play and how to push boundaries. If he is making friends with rough housers, that’s how he is going to play. It doesn’t sound like aggression, it sounds like he needs guidance on proper play.
I would definitely talk with the daycare, see what their methods are on giving corrections. They could be the root of the problem, or it could be a certain mix of dogs that just don’t get along. Some daycares get too many dogs than they can handle and end up having to put many dogs together that shouldn’t be. Combine that with handlers that don’t understand canine body language, and you can damage a dog’s personality! Make sure they don’t use aversive corrections, they should only use positive reinforcement and redirection. If they are the ones who told you your 3mo is aggressive, you might want to seek help elsewhere.