My puppy will be 15 weeks before I can put her into a training class

Hi everyone so I have a 12 week old puppy and I want to get her into training classes to gain important socialization but the classes don’t start until she’ll be 15 weeks. I see many people say the window closes at 16 weeks, so what should I do? Any other ways to socialize her? I’ll keep her in the class but I don’t wanna miss out on this crucial time