I went to an aquarium as a volunteer

Last Thursday, I went to an aquarium with my son's grade Pre-K3 as a volunteer.

It was a great job to for me because I have always wanted to know what the kindergarten life is like. I am curious about how they children play together everyday. At That day, there were 8 mommies working ed as volunteers, each of us had to take care of 2 kids, my responsibility was taking care of my son and another boy named Alston. We gathered at the lobby and headed to the Aquarium by school bus. On the bus, both of us were so excited, kids even sang a lovely song called " baby beluga".

We started visiting by small group when we got there (unclear meaning). We saw a lot of fish and ocean animals, I was so surprised that they children knew so many much of them, they knew call theirs names like shark, seahorse, clown fish, manta ray, jelly fish, eel, dolphin, baby beluga and so on, these two boys even knew these animals' habitual nature and characteristics. I've heard Alston is a naughty boy and his teacher advised him to be good during this field trip day. The fact is my son is that naughty boy not Alston. We had lunch after the dolphin show had finished. Alston is so good, he ate his whole lunch quietly by himself, but my son, he refused to eating and not allowed my eating(unclear meaning). Finally, he ate nothing but only except for a banana.

When we return to school, we mommies were both too all so tired, now I understand it is very hard to be a teacher especially in kindergarten, but it was a good chance for me to experienced kindergarten life. Now I really appreciate the work of the teachers.

Hi, I made some corrections, hope it is ok. Nice piece of writing.

Hi Elaine! It's easier for me to correct here :) 

I went to the aquarium as a volunteer.

Last Thursday, I went to the aquarium with my son's grade Pre-K3 as a volunteer.

It was a great job for me, because I always want to know what the kindergarten life is like. I am curious about how they play together everyday. At That day, there were 8 mommies working as volunteers, each of us had to take care of 2 kids, my responsibility was taking care of my son and another boy named Alston. We gathered at the lobby and headed to the Aquarium by school bus. On the bus, both of us were so excited, the kids even sang a lovely song called " baby beluga".

We started visiting as a small group when we got there. We saw a lot of fish and ocean animals, I was so surprised that they knew so much of them, they can call theirs names like shark, seahorse, clown fish, manta ray, jelly fish, eel, dolphin, baby beluga and so on; these two boys even knew these animals' habitual nature and characteristics. I've heard Alston is a naughty boy and his teacher advised him to be good during this field trip day. The fact is my son is the naughty boy, not Alston. We had lunch after the dolphin show have finished. Alston was so good, he ate his whole lunch quietly by himself, but my son, he refused to eat and was not allowed my food. Finally, he ate nothing but only a banana.

When we returned to school, we mommies were both both of us mommies were too tired, now I understand it is very hard to be a teacher, especially in kindergarten, but it was a good chance for me to experienced kindergarten life. I really appreciate those teachers.

1) We would use "the" because you're not a regular visitor/worker at the aquarium, and aquarium is also just one of those nouns that always needs an article like "an" or "the" before it. 

2) for is the better preposition to use here - we can go over preposition useage in class :) 

3) because in this sentence, "kindergarten life" is a 'subject', you need a verb between it and "like" which is the object. 

4) You could say "That day," or "On that day," 

5) This just be past continuous "were working" OR simple past "8 mommies worked"

6) We use "the" here because it is a specific lobby, and again because it is a specific aquarium and specific kids. 

7) headed is the past tense for "head" 

next paragraph 

6) "as a" would be better here than "by", because it's what the group was LIKE. 

7) It's a specific dolphin show, so we use "the" 

8) We wouldn't use present perfect here because the dolphin show finishing doesn't affect the condition afterwards, so simple past would work well. 

9) Here you're talking about Alston's behaviour during that time, so you would need to use past tense. 

10) without his "whole lunch" might mean everybody's lunch! 

11) We don't use "eating" by itself as an object gerund... "Eating my lunch" as a gerund phrase would be better, but in both of these cases, it's actually better to use the infinitive "to eat" because it was a possible thing that didn't happen. 

12) "nothing but" is the same thing as "only", so choose one or the other. 

13) returned: past tense :) 

14) "Both of us" is a common phrase in English, so I just helped with word order here. 

Great entry! I can see a lot of improvement in your writing!