Which language to learn in school?

It's not that I have this view all of a sudden. I have consistently held a position about this, but it's just that I had to put a strong case to defend my view this time of life. Language is the medium for communicating the content/matter that we wish to send to a or a group of receivers. The question predominantly is around what languages to study at school level. The answer I am trying to make is not universal but valid to Indian context more or less.

English:
I will not spend lot of time on this as there seems to be widespread agreement on why English should be taught at school. It's today world's most popular official language.

Telugu:
Even though I talk about specific language of my own region, logic applies to any other mother tongue. To every language there are two facets-colloquial/spoken and literature/written. Speaking mother tongue is obviously required to operate in the region and to complete day to day chores. Thankfully so far we have not advanced to stage where we use English as household communication language. So I have decent hope that most kids learn speaking Telugu even before going to school. On the written language side these days lot of people are thinking it's unnecessary. If we take emotional side of argument, it's really painful to see people giving less importance to "MOTHER" tongue. On the logical side of argument, purpose of language is to help a person learn more by reading good books in that language. If your mother tongue has vast literature (like telugu) then it is definitely a winning case to learn Telugu at school so that kid gets access to more and more knowledge available in the language.

Hindi:
Hindi is our national language and learning Hindi has a distinctive advantage that person can converse with people in any state using this as medium. Also it's a language with enormous literature.

Sanskrit:
Here comes the most difficult part. In many people's view it's treated as dead language. As per Hindu history, Sanskrit is the language of God's. You can use English to send a money order to someone but if you have a prayer to make to Paramatma, Sanskrit is the language. (Quoting Brahmasri Malladi Chandrasekhara Sastrygaru) Sanskrit is a language that has mantras that have unique power and vibrations that can't be matched by any translations. There are many words in Sanskrit that have no equivalent translation and are used as is when referred to in any other language. (Dharma is one such example)  Sanskrit has so vast literature that includes Vedas, Upanishads, itihasas like Ramayan, Puranas that are embodied with vast knowledge and its surely a case for studying Sanskrit if the purpose of education is acquisition of knowledge.

German/Spanish/French etc:
There is increased interest on including these languages as part of school curriculum. While there is no objection I have personally, few questions need to be considered before enrolling kid in these. 1) will these be useful in future?
2) will there be continuity for these after school so that kid doesn't forget what he learnt. (Either thru interaction or study of language)
3) will it not be burden to kid to learn more in school with already stuffed curriculum.