This is not uncommon, but don't wait too long before considering this option. Beginner students are learning a lot of very basic but very critical information specific to each instrument about how to put together and take apart instruments, how to position their body, hands, fingers, mouth and tongue, plus the unique fingerings that go with each instrument and each note. Switching means a lot of this basic but critical information will have to be re-learned on a different instrument--switching means, for a time, your child will basically be starting all over again. Be sure to talk to your music teacher when considering this option.