(a) Educational corporations of class (w) as defined in section 171 of this act shall have authority to establish and conduct general colleges for furnishing higher learning and to confer such degrees and honors as shall be approved by the state board of education prior to the filing of articles of incorporation; and the term “college” as herein used shall be construed to include any college, university or other institution where the arts, sciences, professions and higher learning are taught and degrees and honors therein conferred. Such colleges may also include preparatory schools as commonly understood;

    (b) Educational corporations of class (x), as defined in section 171, shall have authority to establish and conduct junior colleges, seminaries, academies or preparatory schools, as determined and approved by the state board of education, but not general colleges or universities as defined in subsection (a) hereof;

    (c) Educational corporations of class (z) as defined in said section 171 shall embrace such schools, academies, or colleges as have been heretofore founded under Act 135, Public Acts 1899, known thereunder as “Ursuline academies”; those founded under Act 121, Public Acts 1915, and known thereunder as “ecclesiastical seminaries”; those founded under Act 28, Public Acts 1901, and known thereunder as “Evangelical Lutheran deaf mute institutions”; those founded under Act 135, Public Acts 1867, known as “industrial and charitable schools”; those organized under paragraph (c), subdivision 1, chapter 2, part 4, of Act 84, Public Acts 1921, and such other schools, colleges and institutions of like character and purpose as may be formed under any law of this state for educational purposes shall have all the rights, powers, privileges and immunities enjoyed under its act of incorporation and without regard to the classification made in this act, and upon complying with the provisions hereof shall have such additional rights, powers, privileges and immunities as are conferred hereunder according to the classifications prescribed in this act: Provided further, That any corporation heretofore formed under Act 359, Public Acts 1913, and known thereunder as “kindergarten institutions” shall hereafter be classified under class (x) of section 171 and 172 of this act: Provided further, That any corporation of class (z) hereafter organized under this act may enjoy the privileges provided under classes (w), (x) and (y) of section 171, on condition that it satisfies the requirements set up for corporations of these respective classes.

    (d) Educational corporations of class (y) as defined in section 171 shall have authority to establish and conduct colleges or universities of a graduate rank with programs of studies of 5 years or more.