You definitely need to make your son's third-grade teacher aware of the trauma he went through last year. Knowing about a potential problem can help teachers avoid or overcome them. Rather than criticizing the second-grade teacher, state how your son reacted to the pressure in that classroom to achieve excellence. Be sure to point out how successful the counseling was in restoring his self-esteem.
Now is the time to put into place all the special assistance that your son may need in third grade. This may include more counseling sessions or arranging for tutoring to avoid a repeat of last year's problems. If your son's school has a counselor in the building, it could be helpful to talk to this individual.
Your son is a year older and may have learned a lot about handling school through increased maturity and the counseling sessions. You could be worrying unnecessarily about his facing the same problems this year with a different teacher.
Do plan to talk to him every day so that you get a sense of how things are going at school. Listen carefully to what he is saying -- don't only hear what you think you want to hear. Tell him to always let you know if he is worried about anything that happens during the school day and that you can work on helping him overcome any problems.