change from simple present to simple past tense

Sanjay is correct that in sentence #2, the adverb today must change to some past-tense adverb such as yesterday, but it could also be that day, the day before yesterday, or whatever the actual time phrase should be when transposed into the past tense.

However, in sentence #1, it is incorrect to transpose everyday to yesterday.  These 2 adverbs have completely different meanings.  The past tense sentence should be I went to school everyday, and the context would have been already set out so that the meaning is clear that, in a certain past period, the subject attended school everyday.