When our DD11 was 9 (?) she too was ready for algebra, but the school she was at couldn't fit her into the 8th grade algebra class because of class size restriction laws in FL. She had been radically accelerated at that point into 7th grade and we talked with the algebra teacher about her taking algebra on line while physically sitting in the algebra class so that she could get some instruction on topics she needed clarification on. In order for the school to allow this we had her take the "algebra readiness" test that other 7th graders would take. When her scores came back, it did show some gaps, but it also showed that her thought processing was definitely ready for algebraic thought. Her school used a score of 80% or above to allow admittance into algebra as an 8th grader.
If the score comes back and they say it was too low, I would request to see the test and results and if the score is above 70% ask them what score is permitted - you may find that they use a sliding scale based on who is asking/wanting to get into the class.
I agree with what others are saying though - most gaps in knowledge will be easily filled once they need to use the skills in algebra to solve problems. I wouldn't worry about them at all.
