There are two possibilites:
tenir à + infinitive phrase
tenir à ce que + subject + phrase with verb conjugated in subjunctive
Tenir à + something indicates that you want it to happen, that it is important to you, that you are "anxious" or "keen" for it to come to pass.
When you use this expression to exert your influence over someone else, it requires the subjunctive in the subordinate clause. Actually, you need the subjunctive in the suboordinate for pretty much every expression that you could use to exert your influence over someone else.
Je veux qu'il aille à l'école. = I want him to go to school.
Je tiens à ce qu'il aille à l'école. = I am keen that he go to school, I am anxious that he go to school. (It is important to you that he attend school.)
These sentences have two clauses with separate subjects. In the first clause of the sentence (subject = je), you use the indicative to state your preference or influence (
je veux, je tiens à). Then in the second clause (subject = il) you say what you want him to do, and you must put his desired action in the subjunctive (
qu'il aille à l'école).
What if you aren't talking about what you want someone else to do, but rather what you want to do yourself? In this case, there will be only one subject for both halves of the sentence (=je). You will be expressing a desire for yourself, not stating a preference or influence over someone else's actions. Therefore, you just simply down to an infinitive construction and use
aller à l'école, no subjunctive needed. We simplify in English too. When we switch from "him" to "me," we don't say "I want me to go to school" or "I am anxious that I go to school" but rather "I want to go to school," "I am anxious to go to school."
Je veux aller à l'école. = I want to go to school.
Je tiens à aller à l'école. = I truly wish, I am anxious to go to school. (Going to school is important for you.)
Does that help?
