COPENHAGEN (Reuters) - A 17-year-old Danish girl who offered to fight for Islamic State was sentenced on Monday to eight years in prison by the Danish high court for planning bomb attacks on two schools, one of them Jewish. The high court on Friday found the girl - who was 15 years old at the time - guilty of the offences, upholding an earlier district court ruling. The district court had initially sentenced her to six years in jail.  The prosecutor had called for her to sentenced to preventive detention indefinitely. The girl was arrested at her home in January last year and charged with planning the attacks after acquiring chemicals for making bombs. 