My children are students at the Independent Karate School, which is headquartered in Nashua, NH, but which also offers classes in Merrimack.  Karate schools are a dime a dozen-but not like this one.  The school has been in existence for almost 30 years, and the level of dedication on the part of the adult instructors has to be be seen to be believed.  Instruction is rigorous, but always positive and inspiring, with great attention to safety.  The school's best advertisement of all would be the teenage black belts, who are impressive both as martial artists and as kind, well-grounded individuals.  A real find.