4 month old puppy too rough with new puppy

Question
Nancy,

About a month ago we purchased a 12 week old male cairn terrier (Frodo).  He is extremely energetic and has a lot of trouble playing nicely with our family.  I always keep a constant eye on him because he can quickly get carried away usually by biting someone.  I am enrolled in a puppy training class with him, but he is still very hard to control.  The class leader always just says, "Well, he's a terrier."  Well we just got a female cairn terrier age 12 weeks (Darling).  We have always wanted two dogs so they could play together, and we thought it would be good for Frodo to have another dog to play with.  We also thought it would be a good time to introduce a new puppy since they would only be 1 month apart and could grow up together.  Well the problem is that Frodo plays way too rough with Darling.  He contstantly tries to put his paws on top of her or knocks her feet out from under her.  He doesn't seem to be acting aggressively, he's just so energetic.  I am of course always right there watching them.  I usually remove Frodo from Darling then put him on a leash. I'm not exactly sure what to do because he always wants to play with her, but she'd much rather play with a toy or sniff around her new home.  I don't want to make him resentful or jeolous, but I have to protect the new puppy.  Do you have any suggestions on how I can encourage them to socialize in a positive way.

Answer
Everything you are doing sounds good so far,  the new pup needs a little growing time.  Putting frodo on leash is great,  separating them is also good, for awhile.  Tell Frodo "no" when he gets too rough.  Go to a different trainer, also, one who doesn't have an attitude about terriers.  He is a terrier and needs a different kind of handling.  When you train a terrier you must be more strict on things.  He cannot get away with even moving an inch one way or the other in the wrong direction..  Also they must be challenged If he gets too rough, correct him by putting your hands in back of his neck firmly and saying "no".  The difference with a terrier is, you will have to keep doing this repeatedly until he listens.  NEVER give up and let him win.   Don't be rough just consistent
nancy