What is the ruling on dealing with a national bank for saving money, utilizing the interest to support the national economy and help young people, and is it permissible to leave the principal in the bank without benefiting from the interest?

Good intentions do not permit engaging in usury, because usury is devoid of blessing. It is not permissible to deposit money in usurious banks, whether domestic or foreign, because it constitutes aiding and assisting in usury. What is obligatory is repentance, withdrawing the money, and disposing of the interest in charitable causes.