By a human standard, yes.
So, it is by God's standards, that children are innocents. That's why when Herod ordered the slaughter of babies of a certain age hoping to kill Messiah of prophecy it is referred to as, the slaughter of the innocents.
Children , babies, are innocent. Which is why Jesus said unless we become like little children we shall not see the kingdom of God.
In many cases it is, but not in every case.
All of John 3 is relevant.
We also cannot ignore what He tells us about us: We are ALL sinners.
God is omnipresent. There's your biblically-consistent answer. Was there anything further?
Biblically consistent? I guess you have a point don't you?
God slaughtered innocent first Borns in the old testament. Ordered the unborn to be ripped from the womb, drowned the world, burned to death all living in Sodom and Gomorrah save for one family who he deemed righteous even when the family patriarch offered his virgin daughters for gang rape to save angels from a sexually depraved crowd.
There's a lot else. Interestingly, God killed more people than did Satan, who Omniscience created. And then God sends those he didn't predestine for his grace to the Hell he first created to house Satan and his angels alone . But opened to receive condemned humans God elected not to save before the foundation of the world.
Anything else?
The problem of evil can be explained, but the acceptance of it cannot be imparted.
The darkness and the light. God is all things. Isaiah 45.
After all, you said his being present during this school massacre of adults and innocent childten was biically consistent. Isaiah 45 shows you are right. Nothing that exists is of anything other than the creator.
As you state below this sentence.
God is unlimited and sovereign.
Humans are very limited, and sinners. We can't see the whole picture. I trust that God is good, and that even this will be made right at the judgment. Whether you and others do is not up to me, though I hope you do the same.
Getting your knickers in a twist with me over this is not going to do you any good. If you have an issue with God, take it up with Him.