Practice is not harmful as long as students are successful.
The best way to practice math facts is by saying them aloud to a person who can tell you if you’re wrong or hesitant in your responses. If you are wrong or hesitant, you should practice on that particular fact a bit more until you know it well. This is an effective way to learn anything, including math facts. It is especially valuable if students are given a limited set of facts to learn at each step so they develop and maintain mastery as they learn. If practice is set up carefully, and students get positive feedback showing they are learning and making progress, it is enjoyable and motivating for students. This is the essence of Rocket Math. How in the world could this be harmful? Only by doing it wrong, and doing it wrong specifically in a way that students are not successful.
If teachers skip the practice and learning part and just give the tests–that would be harmful. Students won’t get a chance to learn and will experience failure. The daily oral practice is the heart of Rocket Math–it can’t be skipped!
Daily tests in Rocket Math determine if a student has learned the set of facts he or she is working on, and learned them well enough to have a new set to be added to memory. If students are not proficient in the facts they are working on now (proficient means being able to say a fact and its answer without any hesitation) then they will become overwhelmed with the memorization and will not be successful. So it is critical that teachers are certain (based on the daily tests) that students can answer all the facts up to that point without hesitation. Otherwise they will not be successful and it won’t be enjoyable.
Goals for those daily tests must be based on how quickly students can write. Slow writers must have lower goals. Fast writers must have higher goals. Every student’s goal should be “as fast as her fingers can carry her” and no faster. Arbitrarily raising those goals (expecting faster performance than possible) or arbitrarily lowering those goals (moving students on to the next set before they have mastered the previous set) will cause students to be unsuccessful.
If the checker does not listen and correct errors or hesitations, a student can practice incorrectly and learn the wrong fact. They can also fail to get the tiny bit of extra practice they need on a fact that they can’t quickly remember yet. If practice does not proceed as it should, then students will not learn as they should. Lack of success will make facts practice onerous or counterproductive. The teacher has to monitor students practicing carefully to make sure they are doing it the right way to be successful.
Rocket Math has very explicit instructions here and answers to FAQs here. I have a 3 hour training DVD here. I am available at don@rocketmath.com to answer questions. Practicing math facts ten minutes a day is NOT harmful, if we do it in the way that students are successful.