It is necessary to peruse trust deed 

2) In absence of any rule or clause or requirement of acceptance of resignation, it operates with its tender, if no specific date with respect to its operation is mentioned (see Union of India v. Gopal Chandra Misra 1978 2 SCC 301). If any specific period or a particular date is mentioned in the resignation with respect to its operation, then it becomes effective on the expiry of that particular date or on the expiry of that particular period (see Punjab National Bank v. P.K Mittal. 1989 Supp 2 SCC 175). If such a date or notice period is mentioned in the resignation letter then such a period or date cannot be advanced (see Nand Keshwar Prasad v. Indian Farmers Fertilizers Coop. Ltd. 1998 5 SCC 461). Once it is accepted, no withdrawal is permissible (see Raj Kumar v. Union of India AIR 1969 SC 180). If no specific date is mentioned with respect to its operation and if rule or clause requires its acceptance, then, upon its acceptance it becomes effective

Legal grounds to remove a trustee may include: Violating requirements of the trust agreement. Mismanagement of trust assets, either intentionally or negligently. Fraud or misappropriation of trust assets.

Although trustees have some discretion in managing trust assets, trust agreements usually give the trustees some degree of guidance as to how the assets should be managed as well as the reasons and procedures for removing a trustee. 

the trustee's fiduciary duty, or the obligation to follow the terms of the trust agreement and to act in good faith and in the best interests of the beneficiaries.

A serious conflict between co-trustees can lead to one or more seeking to remove another. If the trustor is still alive, the trustees should express the problem to the trustor and ask that the other trustee be removed. If the trustor is deceased or incapacitated, the trustees should convey the problem to the beneficiaries and ask the beneficiaries to join in seeking removal.

Manager cannot sell land belonging to trust 

2) he is only manager 

3) for sale  of land resolution has to be passed in meeting  of trust 

4) further you may need charity commissioner permission 

- As per law, a  trustee cannot quit without the consent of the court unless the trust means so provides , or except all of the beneficiaries who are judicially capable of doing so consent to the withdrawal.

- Further , the court usually permits the trustee to quit if continuing to serve will be an excessive burden for the trustee, and the resignation will not be significantly harmful to the trust.

- Hence, the other family cannot quit from the trust without a court order or against the consent of all the members

- Further the said manager having no right to sell the property without the consent of all.

- As per , Delhi High Court  no trust property can be held, sold, mortgaged, or exchanged without obtaining prior permission from the court

In general, when members of a trust want to leave the trust, there are certain steps that should be followed:

Review the trust deed: Carefully review the trust deed to understand the provisions related to resignation or removal of trustees and the distribution of trust property.

Compliance with trust deed: Determine if there are any specific procedures or conditions outlined in the trust deed regarding the resignation or removal of trustees. Follow these procedures to ensure compliance with the trust deed.

Resignation of trustees: If the mother and son family want to leave the trust, they can formally resign from their positions as trustees. The trust deed may specify the process for resignation, such as providing written notice to the other trustees or following a particular voting process.

Appointment of new trustees: Once the mother and son family have resigned, new trustees may need to be appointed to maintain the functioning of the trust. The trust deed may outline the procedure for appointing new trustees, which may involve the remaining trustees or other stakeholders.

Share in trust property: If the mother and son family had a 50 percent share in the trust property, their share may need to be transferred to the remaining trustees or the newly appointed trustees. The trust deed should provide guidance on how the transfer of shares or ownership interests in the trust property should be handled.

Legal advice: It is strongly recommended to seek legal advice from a lawyer who specializes in trust and property law. They can review the trust deed, assess the specific circumstances, and guide you through the process of resignation, appointment of new trustees, and the transfer of ownership interests in the trust property.

Regarding the manager of the school selling assets belonging to the school, such as the bus registered in the name of the school, this could potentially be a breach of trust. It is important to take immediate legal action to protect the assets of the trust and prevent any further unauthorized sales or actions that could harm the school's interests.

Then you will be succeeding if you have majority