Learning Korean

I had a spare 10 mins after lunch so I tried to study from a grammar book called "Essential Grammar for Korean as a Second language" - Here is what I studied.

A. Inflect the following verbs as indicated: 

i. 가다 to go 

1) Honorific Head-Suffix (존칭 선행어미): -시- 
The head-suffix ‘시’ elevates the attitude towards the person whom you are talking about (typically the subject of the sentence). This is done independently of the attitude elevation towards the person whom you are talking to, which is typically done by the tail-suffix.

▶ 선생님이 지금 학교에 _____ + ______ + ________.

       stem honorific head-suffix normal closing tail-suffix [FP] 

 Answer
▷ 선생님이 지금 학교에  갑니다 . 
     Teacher is going to school now. 

verb: 가다  definition: 1. to go 2. to go, continue      type: regular verb

declarative present formal high: 갑니다

View all verb conjugations here > 가다 < (dongsa.net)

BUT:  According to the Grammar book note (above) the Honorific should be formed with '시'.

So, should it be '선생님이 지금 학교에가 십니다' ?
- To be honest I am confused - But pretty sure I am right!

                                                              

ii. 먹다 to eat 

2) Tense Head-Suffix (시제 선행어미): -는-, -았/었-, -였-, -더-, -겠- 
Tense Suffixes example 
Past (과거) -았/었-, -였-, -더- 우리는 어제 영화를 보았다.  We saw a movie yesterday. 
Present (현재) -ㄴ/는- * 나는 매일 많이 걷는다.  I walk a lot everyday. 
Future (미래) -겠- 나는 오늘 저녁에 숙제를 하겠다. I will do my homework this evening. 

* The present tense head-suffix is used only for verbs with some tail-suffixes such as 

‘-다’ (normal) or ‘-가’ (interrogative). 

For many other cases, the closing tail-suffix itself indicates the present 

unless there’s a past or future tense head-suffix attached.

 ▶ 아침에 밥을 많이 _____ + _____ + ________.

stem past-tense head-suffix normal closing tail-suffix [FP] 

 ▷ 아침에 밥을 많이 먹었어요. 
      I had a big breakfast this morning. 

verb: 먹다   definition: 1. to eat, to have, to take type: regular verb declarative past informal high 먹었어요 View all verb conjugations here > 먹다 < (dongsa.net)