The midfielder will not play at Southampton on Saturday as he serves his punishment after being pictured in a nightclub following the 4-0 defeat at Everton almost two weeks ago.
Press Association Sport revealed on Monday the 20-year-old would link up with the under-21s again after missing the 3-2 defeat to Watford on Saturday.
Villa are bottom of the Barclays Premier League and seven points from the safety line but Garde will not call on Grealish to help them at St Mary's.
He said: "He has trained this week with the under-21s because it was the plan
He knew that
I know when he might return, he knows as well and when he will I will tell you.
"Like every player Jack made a mistake and he has to pay the consequences for that
If another player does something wrong he will have the same treatment.
"Jack is young and will be back because when he is fully committed in his job he will be a good player."
Ciaran Clark is suspended and Micah Richards is struggling with a knee injury meaning Jores Okore is expected to return in defence while Gabby Agbonlahor could make a comeback after a month out with a calf problem
Garde added: "We are still in a bad position - not a crisis - we know we have to win games and didn't win the last one, we're disappointed because we should have had better result (against Watford).
"The performance of the players pleased me but we made too many mistakes to win."
Source : PA
Source: PA