In, not one, but, two places in the Missouri Constitution:

Article I
BILL OF RIGHTS
Section 7
Public aid for religious purposes–preferences and discriminations on religious grounds.
Section 7. That no money shall ever be taken from the public treasury, directly or indirectly, in aid of any church, sect or denomination of religion, or in aid of any priest, preacher, minister or teacher thereof, as such; and that no preference shall be given to nor any discrimination made against any church, sect or creed of religion, or any form of religious faith or worship.
Source: Const. of 1875, Art. II, § 7.

Article IX
EDUCATION
Section 8
Prohibition of public aid for religious purposes and institutions.
Section 8. Neither the general assembly, nor any county, city, town, township, school district or other municipal corporation, shall ever make an appropriation or pay from any public fund whatever, anything in aid of any religious creed, church or sectarian purpose, or to help to support or sustain any private or public school, academy, seminary, college, university, or other institution of learning controlled by any religious creed, church or sectarian denomination whatever; nor shall any grant or donation of personal property or real estate ever be made by the state, or any county, city, town, or other municipal corporation, for any religious creed, church, or sectarian purpose whatever.
Source: Const. of 1875, Art. XI, § 11.

Well, unless it involves playground materials.

There’s something about that establishment clause that irritates right wingnuts.

A bill introduced yesterday by Representative Hardy Billington (r):

HB 728
Requires the name of the real party in interest to be named in civil actions involving the separation of church and state unless the party in interest is a minor
Sponsor: Billington, Hardy (152)
Proposed Effective Date: 8/28/2019
LR Number: 1693H.01I
Last Action: 01/29/2019 – Introduced and Read First Time (H)
Bill String: HB 728
Next House Hearing: Hearing not scheduled
Calendar: HOUSE BILLS FOR SECOND READING

Wait, don’t right wingnuts keep telling everyone that there is no such thing as “separation of church and state”? Just asking.

The bill text:

FIRST REGULAR SESSION
HOUSE BILL NO. 728 [pdf]
100TH GENERAL ASSEMBLY

INTRODUCED BY REPRESENTATIVE BILLINGTON. 1693H.01I DANA RADEMAN MILLER, Chief Clerk

AN ACT

To repeal section 507.010, RSMo, and to enact in lieu thereof one new section relating to the name of the party in interest in certain civil actions.

Be it enacted by the General Assembly of the state of Missouri, as follows:

Section A. Section 507.010, RSMo, is repealed and one new section enacted in lieu thereof, to be known as section 507.010, to read as follows: 507.010.

1. Except as provided in subsection 2 in this section, every action shall be prosecuted in the name of the real party in interest, but an executor, administrator, personal representative, guardian, conservator, trustee of an express trust, a party with whom or in whose name a contract has been made for the benefit of another, or a party authorized by statute may sue in his own name in such representative capacity without joining with him the party for whose benefit the action is brought; and when a statute so provides, an action for the use or benefit of another shall be brought in the name of the state of Missouri.

2. Except if the party in interest is a minor, in any action involving the separation of church and state, such action shall be prosecuted in the name of the real party in interest.

[emphasis added]

“…2. Except if the party in interest is a minor, in any action involving the separation of church and state, such action shall be prosecuted in the name of the real party in interest.”

That new section is quite a carve out.