That depends completely on what the falsification was and by whom. It also depends on what resulted from the falsification. There is no limit in variations to answer this question. Typically, a false police reports is based upon lies told by law enforcement which become violations of a persons constitutional rights protected by the 14th Amendment. As well the falsehood becomes the power station of a properly prepared criminal defense.
If your question is based on a different perspective it will have a different answer. I hope this was helpful.
I practice in Michigan where one can be prosecuted as an adult at the age of 17. If you are indeed a minor or an adult and break the law it doesn't matter; you broke the law. The only issue is whether your case is handled in the juvenile court or adult court arena. Many states, such as Michigan, distinguish between False Police Report of a Misdemeanor and False Report of a Felony. As one might guess the former is a misdemeanor offense and the latter is a felony offense. Again, if you are a minor and have no prior record you are probably not going to prison, jail or the juvenile detention facility. However, you can expect to be placed on probation, supervised and pay fines, costs and probation oversight fees. If chargd you should be appointed an attorney and you can discuss the case with him/her and your options and any plea agreements.