Signing in with Google (or any social login) creates a new Tinkercad account when you sign in for the first time. Here is how you and your students who have a Google sign on can sign into Tinkercad with your Google credentials.
1. On Tinkercad.com, click "Sign In".
2. In the next screen, click "Sign in using Social Providers".
3. Then, click "Google" to sign in, which will create a new account when you sign in with Google credentials for the first time.