Struggling to understand the particle choice here…
母は娘におもちゃを片付けさせます
母は娘を学校に行かせます
In the first example, に is being used since the command was directed at the daughter. Why in the second example is the command not also directed at the daughter. Aka…
母は娘に学校に行かせます
2 comments
In your first example, に is used because the daughter is mostly the one doing the action, and therefore the verb that the mother does is less of the focus (I.e. the main action in the clause is the cleaning up of the toys).
In you second example, を is used because the mother is the one doing the direct action (sending the daughter to school). You could say that the daughter is the one doing it (since the base verb is ‘to go’) and translate it as ‘makes her daughter go to school,’ but when you look at it, ‘go’ in that sentence is less focused on than ‘makes.’
You can also tell which verb the focus is on by looking at the other (next) particle used. In your first example, を is used because the daughter is directly affecting the おもちゃ. In your second example, に is used because the daughter is not directly affecting the 学校. The direct object particle (を) usually indicates the verb in focus.
TL;DR you can think of it as when one particle is used in one spot, the other particle is used in the other spot
(Edit) Also notice that in the first example, the action is happening to the toys, while in the second example, the action is happening to the daughter.
(Edited for typos)
The basic rule of thumb is that in the case of a transitive verb, the direction of the causative gets “〜に” and in intransitive verbs it gets “〜を” but this rule is not absolute and “〜に” can sometimes also be seen with intransitive verbs as well.