the teacher was nice.Unlike my 2nd grade teacher.
>> Unlike my 2nd grade teacher, my 3rd grade teacher is nice.
-You are describing a person, so you will use present tense unless, if you are saying that your teacher was nice before but now she is not.

we did bingo alot, and we made name tags.
>> We did a lot of Bingo, and we made name tags.
-Remember that you must always cstart your sentence with a capital letter.

I love my teacher.
>>CORRECT!

And my gymnastic teacher was VERY SCARY.
>> On the other hand, my gymnast teacher was very scary.

my sister told me that.
>> My sister told me that.