Chairman of a trust can change Managing Trustee

sir,
In a private Educational Trust of 3 numbers of Trustee, 1 number of Managing Trustee cum Secretary and 1 number of Chairman, there is a clause in the Trust Deed that 2/3 members of the Trustee Board can take any decision in a meeting and effect that decision. my question is that only 3 trustees out of 5 trustees can remove or Change Managing Trustee cum Secretary. will it be valid in the eye of law.