After the subject or an auxiliary if there is one. So "I am a student and I also give classes" is correct.

Hey Lucile, The correct sentence is the first one "I am a student and I also give classes". That is because you usually use "also" in front of a verb. However, there are some cases in which the position of the word "also" may change. I shall provide you with an explanation of the usage of "also" and its alternating positions in sentences: * Firstly, you should know that you use "also" when you are giving more information about something. 1) "Also" is usually used in front of a verb. If there is no auxiliary verb, you put 'also' immediately in front of the verb, unless the verb is 'be'. E.g.: "I also began to be interested in sports". E.g.: "They also helped me out". 2) If the verb is 'be', you put 'also' after it. E.g.: "I was also an American". 3) If there is an auxiliary verb, you put 'also' after the auxiliary verb. E.g.: "The symptoms of the illness were also described in the book". 4) If there is more than one auxiliary verb, you put 'also' after the first one. E.g.: "We'll also be learning about healthy eating". 5) 'Also' is sometimes put at the beginning of a clause. E.g.: "She is very intelligent. Also, she is kind!" *** Be Careful! Do not put 'also' at the end of a clause. Hope that helps!!! :) Should you have any further doubts, do not hesitate to contact me. I shall be pleased to help!