Does an Employee needs Employer's permission to pursure bachelor's or Masters degree from distance.

While leaving office today, I informed my boss that I might not be coming Tommorow as tomorrow is my MCA exam of third semester (from IGNOU). He asked me whether I took permission in written or not. I was silent as I didn't knew it's mandatory though I have discussed it with him verbally before talking admission in MCA. I'm quite surprised. I just want to know is there a rule like this that I have to take permission in written ?

Edit : It's a small Startup. We're barely a team of 10 members.