(3) The discontinuance or substitution of an institutional educational measure by another type of institutional educational measure shall be subject to the following restrictions: a) Enforcement of the educational measure of committal to an educational institution may not be discontinued before the expiration of a term of six months, and until such time may only be substituted by the educational measure of committal to an educational-reformatory home or the educational measure of committal to some other training institution; b) Enforcement of the educational measure of committal to an educational-reformatory home may not be discontinued before the expiration of a term of one year, and before such time may only be substituted by the educational measure of a committal to some other training institution. (4) Exceptionally, enforcement of the educational measure of committal to educational institution or the educational measure of committal to an educational-reformatory home may be discontinued or be substituted by some other measure even before the expiration of the deadlines referred to in paragraph 3, items a) and b) of this Article if special circumstances that relate to the personality of the juvenile manifestly show that the purpose of these measures has been attained. Article 98 Reconsideration of Educational Measures (1) The court shall reconsider the need of enforcing the educational measure imposed if more than one year has elapsed since the day when the decision imposing an educational measure of intensified supervision or an institutional educational measure came into force, and if until such time the enforcement of the measure has not commenced. Reconsidering it, the court may decide that the previously imposed measure be enforced, not enforced or substituted with another measure. (2) The educational measure of committal to a disciplinary centre for juveniles shall not be executed if more than six months have elapsed since the day when the decision imposing the measure came into force, and if the enforcement of the measure has not yet commenced. Article 99 Punishment of Senior Juveniles Punished may be only a criminally responsible senior juvenile, who has perpetrated a criminal offence for which a punishment of imprisonment for a term exceeding five years has been prescribed and if it would not be justifiable to apply an educational measure because of the grave consequences of the offence perpetrated and the high degree of criminal responsibility. Article 100 Juvenile Imprisonment (1) The duration of the punishment of juvenile imprisonment may not be shorter than one or longer than ten years, and shall be imposed in full years or half-years. (2) In meting out punishment for a senior juvenile for a criminal offence, the court may not impose juvenile imprisonment for a term exceeding that of imprisonment prescribed for that particular criminal offence, but the court shall not be bound by the minimal measure of that punishment prescribed. Article 101 Meting Out Juvenile Imprisonment In meting out juvenile imprisonment for a senior juvenile, the court shall take into consideration all circumstances that may influence the punishment being longer or shorter (Article 49, General Principles of Meting out Punishments), paying special attention to level of mental development of the juvenile and time needed for his correction and occupational training. Article 102 Imposing Educational Measures and Juvenile Imprisonment for Concurrent Criminal Offences 30