I am learning causative forms here
先生が参加させてくれました Teacher allowed me to participate
what does 先生が参加させてもらいました mean?
But there's an area of caution here. If the second sentence it indeed supposed to be 先生 が... , then it means "the teacher was allowed to participate".
However, my inclination is that the second sentence is really supposed to be 先生 に... , in which case it would mean roughly the same thing as the first sentence: The teacher allowed me to participate. However, as I mentioned, in this case, the focus is more on the act of you receiving permission from the teacher, rather than on the teacher's (kind) act of allowing you to participate.
For more information on the distinctions between