I think we would all agree that a school is a high place because they purpose to raise the education level of its students to make them better human beings. We actually call colleges and universities places of higher education.
The issue of what should be taught in school came up with respect to religion. My response follows.
A school is a place for truth. And the truth is that there is only one God and His name is Jesus. Isa 45:5 Deu 6:4 Joh 14:9 2Ti 4:1 Mat 28:18 Act 16:31
To give time, space or place to the devil is a recipe for disaster. It is evidence that the person who would allow such is doubleminded. It deemphasises the fact that there is salvation in no other name under heaven than Christ Jesus. Act 4:12
You can't force a person to believe but you can force them to hear and recite. This goes on all the time with liberal education where conservative students are forced to regurgitate answers reflecting liberal ideology.
The Old Testament proves over and over again that allowing other gods inevitably pollutes the whole land. The very first commandment is 'you shall have no other gods before me". This means that Jesus Christ must be lifted up to His rightful place above all other religions or ideologies. This is a commandment and not a recommendation.
Often in the Old Testament a good king would arise in Israel after a bad king and that good king would correct some of the ills the bad king had instituted but most every time the good king would fail to tear down the altars and high places of the false gods. Num 33:52 2Ki 12:3 2Ki 15:35
This reflected the flawed 'goodness' of the good king. He was tolerant.
But there were some good kings who actually did what was in their heart. 2Ki 23:19
As said before, you can't force a person to believe, but you can make sure they are informed. That is what preaching the Gospel is all about - not converting people but making sure they have heard the truth.
Just as the conservative student in a liberal school is free to believe whatever they want despite what they are taught, so a liberal student in a conservative school would be free to believe what they wanted.
Furthermore, they would be able to voice their unbelief. They simply would not be able to administratively change the truth of God into a lie. Rom 1:25
It is time for a 'really' good king to sit on the throne. Maybe there will be none until Jesus takes the throne but we have it within our power to establish our institutions in truth. Do we have the will?