According to Google Ngrams, 'educational field' has been used more often in the past 100 years, but, strange to say, it is seen only as frequently as 'education field' lately.
That aside, it should be noted that 'field of education' is used much more than either of those two expressions.
how long you have been in the educational field
How long you have been in the educational field?
Better:
How long have you been teaching?
educational field
because think of science field and scientific field, scientific field sounds better
but i'm not an expert
According to Google Ngrams, 'educational field' has been used more often in the past 100 years, but, strange to say, it is seen only as frequently as 'education field' lately.
That aside, it should be noted that 'field of education' is used much more than either of those two expressions.
https://books.google.com/ngrams/graph?content=education+field%2Ceducational+field%2Cfield+of+education&year_start=1800&year_end=2018&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Ceducation%20field%3B%2Cc0%3B.t1%3B%2Ceducational%20field%3B%2Cc0%3B.t1%3B%2Cfield%20of%20education%3B%2Cc0
CJ
Still employed but looking to expand my knowledge in the educational field.
Help is needed in the educational field vs in the education field
educational
CJ