"I usually go to school by bus but today I went on foot." "I usually go to school by bus but today I am going on foot." Which sentence is wrong? I think both of them are correct. But someone told me that I was wrong.
The only thing wrong with either sentence is that there should be a comma after the word bus to separate the two clauses.
The first sentence uses past tense (went) and the other uses (am going), which could be present progressive or future, depending on whether you are actually walking now.
But both sentences seem less likely than
I usually take/ride the bus to school, but today I'm walking.