This is a first offense, no prior record of any kind, stupid kid thing to do.
A juvenile conviction for assault 4 with sexual motivation is a gross misdemeanor. The most direct consequence is the court can impose a certain sanction. In Washington, juvenile offenses carry a “standard range” that is based on the disposition offense category and also the number of prior convictions, if any. The standard range for assault in the 4th degree with sexual motivation is the same as the standard range for an assault in the 4th degree without any special allegation — the range is called “local sanctions.” Local sanctions is a range of penalties that include anywhere from 0 to 12 months of community supervision (probation), 0 to 150 hours of community service work, 0 to $500 fine, and/or 0 to 30 days confinement. The judge decides where within that range an offender is sentenced. If the law and facts support going outside the range, the judge can do that too.
The sexual motivation tag is something that might trigger the court to impose a sexual deviancy evaluation and follow up treatment that would be a condition of community supervision. That allegation might also affect other conditions of community supervision depending upon the underling facts.
Although assault 4 with sexual motivation sounds like a sex offense it is not; at least, as the law is currently written. That means an offender does not have to register as a sex offender and also can get the record sealed in as little as two years if certain conditions are met (most importantly no reoffending). However, until that time, members of the public can view the court file and the conviction and the existence of this conviction could present problems in other areas such as gaining certain types of employment.
DISCLAIMER: This is NOT legal advice and is not intended for the reader to proceed in reliance on this information. The reader should always consult with an attorney regarding these specific questions as they pertain to the specific facts of his/her case.